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• How to bind dropdownlist data to complex class?

  - by chobo2

  Hi I am using asp.net mvc 2.0(default binding model) and I have this problem. I have a strongly typed view that has a dropdownlist <%= Html.DropDownList("List", "-----")%> Now I have a model class like Public class Test() { public List { get; set; } public string Selected {get; set;} } Now I have in my controller this public ActionResult TestAction() { Test ViewModel = new Test(); ViewModel.List = new SelectList(GetList(), "value", "text", "selected"); return View(Test); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult TestAction(Test ViewModel) { return View(); } Now when I load up the TestAction page for the first time it populates the dropdown list as expected. Now I want to post the selected value back to the server(the dropdownlist is within a form tag with some other textboxes). So I am trying to bind it automatically when it comes in as seen (Test ViewModel) However I get this big nasty error. Server Error in '/' Application. No parameterless constructor defined for this object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.MissingMethodException: No parameterless constructor defined for this object. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [MissingMethodException: No parameterless constructor defined for this object.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98 System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241 System.Activator.CreateInstance(Type type, Boolean nonPublic) +69 System.Activator.CreateInstance(Type type) +6 System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) +403 System.Web.Mvc.DefaultModelBinder.BindSimpleModel(ControllerContext controllerContext, ModelBindingContext bindingContext, ValueProviderResult valueProviderResult) +544 System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +479 System.Web.Mvc.DefaultModelBinder.GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder) +45 System.Web.Mvc.DefaultModelBinder.BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor) +658 System.Web.Mvc.DefaultModelBinder.BindProperties(ControllerContext controllerContext, ModelBindingContext bindingContext) +147 System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model) +98 System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +2504 System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +548 System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +474 System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +181 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +830 System.Web.Mvc.Controller.ExecuteCore() +136 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +111 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +39 System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__4() +65 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +44 System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +42 System.Web.Mvc.Async.WrappedAsyncResult`1.End() +141 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +54 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +52 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8836913 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184 So how can I do this?

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• Partial generic type inference possible in C#?

  - by Lasse V. Karlsen

  I am working on rewriting my fluent interface for my IoC class library, and when I refactored some code in order to share some common functionality through a base class, I hit upon a snag. Note: This is something I want to do, not something I have to do. If I have to make do with a different syntax, I will, but if anyone has an idea on how to make my code compile the way I want it, it would be most welcome. I want some extension methods to be available for a specific base-class, and these methods should be generic, with one generic type, related to an argument to the method, but the methods should also return a specific type related to the particular descendant they're invoked upon. Better with a code example than the above description methinks. Here's a simple and complete example of what doesn't work: using System; namespace ConsoleApplication16 { public class ParameterizedRegistrationBase { } public class ConcreteTypeRegistration : ParameterizedRegistrationBase { public void SomethingConcrete() { } } public class DelegateRegistration : ParameterizedRegistrationBase { public void SomethingDelegated() { } } public static class Extensions { public static ParameterizedRegistrationBase Parameter<T>( this ParameterizedRegistrationBase p, string name, T value) { return p; } } class Program { static void Main(string[] args) { ConcreteTypeRegistration ct = new ConcreteTypeRegistration(); ct .Parameter<int>("age", 20) .SomethingConcrete(); // <-- this is not available DelegateRegistration del = new DelegateRegistration(); del .Parameter<int>("age", 20) .SomethingDelegated(); // <-- neither is this } } } If you compile this, you'll get: 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingConcrete' and no extension method 'SomethingConcrete'... 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingDelegated' and no extension method 'SomethingDelegated'... What I want is for the extension method (Parameter<T>) to be able to be invoked on both ConcreteTypeRegistration and DelegateRegistration, and in both cases the return type should match the type the extension was invoked on. The problem is as follows: I would like to write: ct.Parameter<string>("name", "Lasse") ^------^ notice only one generic argument but also that Parameter<T> returns an object of the same type it was invoked on, which means: ct.Parameter<string>("name", "Lasse").SomethingConcrete(); ^ ^-------+-------^ | | +---------------------------------------------+ .SomethingConcrete comes from the object in "ct" which in this case is of type ConcreteTypeRegistration Is there any way I can trick the compiler into making this leap for me? If I add two generic type arguments to the Parameter method, type inference forces me to either provide both, or none, which means this: public static TReg Parameter<TReg, T>( this TReg p, string name, T value) where TReg : ParameterizedRegistrationBase gives me this: Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Which is just as bad. I can easily restructure the classes, or even make the methods non-extension-methods by introducing them into the hierarchy, but my question is if I can avoid having to duplicate the methods for the two descendants, and in some way declare them only once, for the base class. Let me rephrase that. Is there a way to change the classes in the first code example above, so that the syntax in the Main-method can be kept, without duplicating the methods in question? The code will have to be compatible with both C# 3.0 and 4.0. Edit: The reason I'd rather not leave both generic type arguments to inference is that for some services, I want to specify a parameter value for a constructor parameter that is of one type, but pass in a value that is a descendant. For the moment, matching of specified argument values and the correct constructor to call is done using both the name and the type of the argument. Let me give an example: ServiceContainerBuilder.Register<ISomeService>(r => r .From(f => f.ConcreteType<FileService>(ct => ct .Parameter<Stream>("source", new FileStream(...))))); ^--+---^ ^---+----^ | | | +- has to be a descendant of Stream | +- has to match constructor of FileService If I leave both to type inference, the parameter type will be FileStream, not Stream.

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• Qt - reloading widget contents

  - by bullettime

  I'm trying to modify the fridge magnets example by adding a button that will reload the widget where the draggable labels are drawn, reflecting any changes made to the text file it reads. I defined another class that would contain the button and the DragWidget object, so there would be an instance of this class instead of DragWidget in main(): class wrapWidget: public QWidget { public: wrapWidget(); }; wrapWidget::wrapWidget() { QGridLayout *gridlayout = new QGridLayout(); DragWidget *w = new DragWidget(); QPushButton *b = new QPushButton("refresh"); gridlayout ->addWidget(w,0,0); gridlayout ->addWidget(b,1,0); setLayout(gridlayout ); connect(b,SIGNAL(clicked()),w,SLOT(draw())); } The call to connect is where I'm trying to do the refresh thing. In the original fridge magnets example, all the label drawing code was inside the constructor of the DragWidget class. I moved that code to a public method that I named 'draw()', and called this method from the constructor instead. Here's DragWidget definition and implementation: #include <QWidget> QT_BEGIN_NAMESPACE class QDragEnterEvent; class QDropEvent; QT_END_NAMESPACE class DragWidget : public QWidget { public: DragWidget(QWidget *parent = 0); public slots: void draw(); protected: void dragEnterEvent(QDragEnterEvent *event); void dragMoveEvent(QDragMoveEvent *event); void dropEvent(QDropEvent *event); void mousePressEvent(QMouseEvent *event); void paintEvent(QPaintEvent *event); }; DragWidget::DragWidget(QWidget *parent) : QWidget(parent) { draw(); QPalette newPalette = palette(); newPalette.setColor(QPalette::Window, Qt::white); setPalette(newPalette); setMinimumSize(400, 100);//qMax(200, y)); setWindowTitle(tr("Fridge Magnets")); setAcceptDrops(true); } void DragWidget::draw(){ QFile dictionaryFile(":/dictionary/words.txt"); dictionaryFile.open(QFile::ReadOnly); QTextStream inputStream(&dictionaryFile); int x = 5; int y = 5; while (!inputStream.atEnd()) { QString word; inputStream >> word; if (!word.isEmpty()) { DragLabel *wordLabel = new DragLabel(word, this); wordLabel->move(x, y); wordLabel->show(); wordLabel->setAttribute(Qt::WA_DeleteOnClose); x += wordLabel->width() + 2; if (x >= 245) { x = 5; y += wordLabel->height() + 2; } } } } I thought that maybe calling draw() as a slot would be enough to reload the labels, but it didn't work. Putting the draw() call inside the widget's overriden paintEvent() instead of the constructor didn't work out as well, the program would end up in an infinite loop. What I did was obviously not the right way of doing it, so what should I be doing instead?

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• Problem with memset after an instance of a user defined class is created and a file is opened

  - by Liberalkid

  I'm having a weird problem with memset, that was something to do with a class I'm creating before it and a file I'm opening in the constructor. The class I'm working with normally reads in an array and transforms it into another array, but that's not important. The class I'm working with is: #include <vector> #include <algorithm> using namespace std; class PreProcess { public: PreProcess(char* fileName,char* outFileName); void SortedOrder(); private: vector< vector<double > > matrix; void SortRow(vector<double> &row); char* newFileName; vector< pair<double,int> > rowSorted; }; The other functions aren't important, because I've stopped calling them and the problem persists. Essentially I've narrowed it down to my constructor: PreProcess::PreProcess(char* fileName,char* outFileName):newFileName(outFileName){ ifstream input(fileName); input.close(); //this statement is inconsequential } I also read in the file in my constructor, but I've found that the problem persists if I don't read in the matrix and just open the file. Essentially I've narrowed it down to if I comment out those two lines the memset works properly, otherwise it doesn't. Now to the context of the problem I'm having with it: I wrote my own simple wrapper class for matrices. It doesn't have much functionality, I just need 2D arrays in the next part of my project and having a class handle everything makes more sense to me. The header file: #include <iostream> using namespace std; class Matrix{ public: Matrix(int r,int c); int &operator()(int i,int j) {//I know I should check my bounds here return matrix[i*columns+j]; } ~Matrix(); const void Display(); private: int *matrix; const int rows; const int columns; }; Driver: #include "Matrix.h" #include <string> using namespace std; Matrix::Matrix(int r,int c):rows(r),columns(c) { matrix=new int[rows*columns]; memset(matrix,0,sizeof(matrix)); } const void Matrix::Display(){ for(int i=0;i<rows;i++){ for(int j=0;j<columns;j++) cout << (*this)(i,j) << " "; cout << endl; } } Matrix::~Matrix() { delete matrix; } My main program runs: PreProcess test1(argv[1],argv[2]); //test1.SortedOrder(); Matrix test(10,10); test.Display(); And when I run this with the input line uncommented I get: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371727776 32698 -1 0 0 0 0 0 6332656 0 -1 -1 0 0 6332672 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371732704 32698 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I really don't have a clue what's going on in memory to cause this, on a side note if I replace memset with: for(int i=0;i<rows*columns;i++) *(matrix+i) &= 0x0; Then it works perfectly, it also works if I don't open the file. If it helps I'm running GCC 64-bit version 4.2.4 on Ubuntu.I assume there's some functionality of memset that I'm not properly understanding.

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• Is it a missing implementation with JPA implementation of hibernate??

  - by Jegan

  Hi all, On my way in understanding the transaction-type attribute of persistence.xml, i came across an issue / discrepency between hibernate-core and JPA-hibernate which looks weird. I am not pretty sure whether it is a missing implementation with JPA of hibernate. Let me post the comparison between the outcome of JPA implementation and the hibernate implementation of the same concept. Environment Eclipse 3.5.1 JSE v1.6.0_05 Hibernate v3.2.3 [for hibernate core] Hibernate-EntityManger v3.4.0 [for JPA] MySQL DB v5.0 Issue 1.Hibernate core package com.expt.hibernate.core; import java.io.Serializable; public final class Student implements Serializable { private int studId; private String studName; private String studEmailId; public Student(final String studName, final String studEmailId) { this.studName = studName; this.studEmailId = studEmailId; } public int getStudId() { return this.studId; } public String getStudName() { return this.studName; } public String getStudEmailId() { return this.studEmailId; } private void setStudId(int studId) { this.studId = studId; } private void setStudName(String studName) { this.studName = stuName; } private void setStudEmailId(int studEmailId) { this.studEmailId = studEmailId; } } 2. JPA implementaion of Hibernate package com.expt.hibernate.jpa; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name = "Student_Info") public final class Student implements Serializable { @Id @GeneratedValue @Column(name = "STUD_ID", length = 5) private int studId; @Column(name = "STUD_NAME", nullable = false, length = 25) private String studName; @Column(name = "STUD_EMAIL", nullable = true, length = 30) private String studEmailId; public Student(final String studName, final String studEmailId) { this.studName = studName; this.studEmailId = studEmailId; } public int getStudId() { return this.studId; } public String getStudName() { return this.studName; } public String getStudEmailId() { return this.studEmailId; } } Also, I have provided the DB configuration properties in the associated hibernate-cfg.xml [in case of hibernate core] and persistence.xml [in case of JPA (hibernate entity manager)]. create a driver and perform add a student and query for the list of students and print their details. Then the issue comes when you run the driver program. Hibernate core - output Exception in thread "main" org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.core.Student at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:84) at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:100) at org.hibernate.tuple.entity.AbstractEntityTuplizer.instantiate(AbstractEntityTuplizer.java:351) at org.hibernate.persister.entity.AbstractEntityPersister.instantiate(AbstractEntityPersister.java:3604) .... .... This exception is flashed when the driver is executed for the first time itself. JPA Hibernate - output First execution of the driver on a fresh DB provided the following output. DEBUG SQL:111 - insert into student.Student_Info (STUD_EMAIL, STUD_NAME) values (?, ?) 17:38:24,229 DEBUG SQL:111 - select student0_.STUD_ID as STUD1_0_, student0_.STUD_EMAIL as STUD2_0_, student0_.STUD_NAME as STUD3_0_ from student.Student_Info student0_ student list size == 1 1 || Jegan || [email protected] second execution of the driver provided the following output. DEBUG SQL:111 - insert into student.Student_Info (STUD_EMAIL, STUD_NAME) values (?, ?) 17:40:25,254 DEBUG SQL:111 - select student0_.STUD_ID as STUD1_0_, student0_.STUD_EMAIL as STUD2_0_, student0_.STUD_NAME as STUD3_0_ from student.Student_Info student0_ Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.jpa.Student at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:614) at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:76) at driver.StudentDriver.main(StudentDriver.java:43) Caused by: org.hibernate.InstantiationException: No default constructor for entity: com.expt.hibernate.jpa.Student .... .... Could anyone please let me know if you have encountered this sort of inconsistency? Also, could anyone please let me know if the issue is a missing implementation with JPA-Hibernate? ~ Jegan

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• Android: Programatically Add UI Elements to a View

  - by Shivan Raptor

  My view is written as follow: package com.mycompany; import android.view.View; import java.util.concurrent.TimeUnit; import java.util.ArrayList; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.util.AttributeSet; import android.graphics.Paint; import android.graphics.Point; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.widget.*; public class GameEngineView extends View implements SensorEventListener { GameLoop gameloop; String txt_acc; float accY; ArrayList<Point> bugPath; private SensorManager sensorManager; private class GameLoop extends Thread { private volatile boolean running = true; public void run() { while (running) { try { TimeUnit.MILLISECONDS.sleep(1); postInvalidate(); pause(); } catch (InterruptedException ex) { running = false; } } } public void pause() { running = false; } public void start() { running = true; run(); } public void safeStop() { running = false; interrupt(); } } public void unload() { gameloop.safeStop(); } public GameEngineView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); // TODO Auto-generated constructor stub init(context); } public GameEngineView(Context context, AttributeSet attrs) { super(context, attrs); // TODO Auto-generated constructor stub init(context); } public GameEngineView(Context context) { super(context); // TODO Auto-generated constructor stub init(context); } private void init(Context context) { txt_acc = ""; // Adding SENSOR sensorManager=(SensorManager)context.getSystemService(Context.SENSOR_SERVICE); // add listener. The listener will be HelloAndroid (this) class sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); // Adding UI Elements : How ? Button btn_camera = new Button(context); btn_camera.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, LinearLayout.LayoutParams.FILL_PARENT)); btn_camera.setClickable(true); btn_camera.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { System.out.println("clicked the camera."); } }); gameloop = new GameLoop(); gameloop.run(); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // TODO Auto-generated method stub //super.onMeasure(widthMeasureSpec, heightMeasureSpec); System.out.println("Width " + widthMeasureSpec); setMeasuredDimension(widthMeasureSpec, heightMeasureSpec); } @Override protected void onDraw(Canvas canvas) { // TODO Auto-generated method stub // super.onDraw(canvas); Paint p = new Paint(); p.setColor(Color.WHITE); p.setStyle(Paint.Style.FILL); p.setAntiAlias(true); p.setTextSize(30); canvas.drawText("|[ " + txt_acc + " ]|", 50, 500, p); gameloop.start(); } public void onAccuracyChanged(Sensor sensor,int accuracy){ } public void onSensorChanged(SensorEvent event){ if(event.sensor.getType()==Sensor.TYPE_ACCELEROMETER){ //float x=event.values[0]; accY =event.values[1]; //float z=event.values[2]; txt_acc = "" + accY; } } } I would like to add a Button to the scene, but I don't know how to. Can anybody give me some lights? UPDATE: Here is my Activity : public class MyActivity extends Activity { private GameEngineView gameEngine; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // add Game Engine gameEngine = new GameEngineView(this); setContentView(gameEngine); gameEngine.requestFocus(); } }

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• java.lang.OutOfMemoryError: bitmap size exceeds VM budget

  - by Angel

  Hi, I am trying to change the layout of my application from portrait to landscape and vice-versa. But if i do it frequently or more than once then at times my application crashes.. Below is the error log. Please suggest what can be done? < 01-06 09:52:27.787: ERROR/dalvikvm-heap(17473): 1550532-byte external allocation too large for this process. 01-06 09:52:27.787: ERROR/dalvikvm(17473): Out of memory: Heap Size=6471KB, Allocated=4075KB, Bitmap Size=9564KB 01-06 09:52:27.787: ERROR/(17473): VM won't let us allocate 1550532 bytes 01-06 09:52:27.798: DEBUG/skia(17473): --- decoder-decode returned false 01-06 09:52:27.798: DEBUG/AndroidRuntime(17473): Shutting down VM 01-06 09:52:27.798: WARN/dalvikvm(17473): threadid=3: thread exiting with uncaught exception (group=0x4001e390) 01-06 09:52:27.807: ERROR/AndroidRuntime(17473): Uncaught handler: thread main exiting due to uncaught exception 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): java.lang.RuntimeException: Unable to start activity ComponentInfo{}: android.view.InflateException: Binary XML file line #2: Error inflating class 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2596) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2621) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3812) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.access$2300(ActivityThread.java:126) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1936) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.os.Handler.dispatchMessage(Handler.java:99) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.os.Looper.loop(Looper.java:123) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.main(ActivityThread.java:4595) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Method.invokeNative(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Method.invoke(Method.java:521) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at dalvik.system.NativeStart.main(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: android.view.InflateException: Binary XML file line #2: Error inflating class 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createView(LayoutInflater.java:513) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:56) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:563) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:385) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:320) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.inflate(LayoutInflater.java:276) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:207) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.Activity.setContentView(Activity.java:1629) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at onCreate(Game.java:98) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2544) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 12 more 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: java.lang.reflect.InvocationTargetException 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.widget.LinearLayout.(LinearLayout.java:92) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Constructor.constructNative(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at java.lang.reflect.Constructor.newInstance(Constructor.java:446) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.LayoutInflater.createView(LayoutInflater.java:500) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 22 more 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): Caused by: java.lang.OutOfMemoryError: bitmap size exceeds VM budget 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:464) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:340) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:697) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.content.res.Resources.loadDrawable(Resources.java:1705) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.content.res.TypedArray.getDrawable(TypedArray.java:548) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.View.(View.java:1850) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.View.(View.java:1799) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): at android.view.ViewGroup.(ViewGroup.java:296) 01-06 09:52:27.857: ERROR/AndroidRuntime(17473): ... 26 more

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• Why is the this-pointer needed to access inherited attributes?

  - by Shadow

  Hi, assume the following class is given: class Base{ public: Base() {} Base( const Base& b) : base_attr(b.base_attr) {} void someBaseFunction() { .... } protected: SomeType base_attr; }; When I want a class to inherit from this one and include a new attribute for the derived class, I would write: class Derived: public Base { public: Derived() {} Derived( const Derived& d ) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void SomeDerivedFunction() { .... } private: SomeOtherType derived_attr; }; This works for me (let's ignore eventually missing semicolons or such please). However, when I remove the "this-" in the copy constructor of the derived class, the compiler complains that "'base_attr' was not declared in this scope". I thought that, when inheriting from a class, the protected attributes would then also be accessible directly. I did not know that the "this-" pointer was needed. I am now confused if it is actually correct what I am doing there, especially the copy-constructor of the Derived-class. Because each Derived object is supposed to have a base_attr and a derived_attr and they obviously need to be initialized/set correctly. And because Derived is inheriting from Base, I don't want to explicitly include an attribute named "base_attr" in the Derived-class. IMHO doing so would generally destroy the idea behind inheritance, as everything would have to be defined again. EDIT Thank you all for the quick answers. I completely forgot the fact that the classes actually are templates. Please, see the new examples below, which are actually compiling when including "this-" and are failing when omiting "this-" in the copy-constructor of the Derived-class: Base-class: #include <iostream> template<class T> class Base{ public: Base() : base_attr(0) {} Base( const Base& b) : base_attr(b.base_attr) {} void baseIncrement() { ++base_attr; } void printAttr() { std::cout << "Base Attribute: " << base_attr << std::endl; } protected: T base_attr; }; Derived-class: #include "base.hpp" template< class T > class Derived: public Base<T>{ public: Derived() : derived_attr(1) {} Derived( const Derived& d) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void derivedIncrement() { ++derived_attr; } protected: T derived_attr; }; and for completeness also the main function: #include "derived.hpp" int main() { Derived<int> d; d.printAttr(); d.baseIncrement(); d.printAttr(); Derived<int> d2(d); d2.printAttr(); return 0; }; I am using g++-4.3.4. Although I understood now that it seems to come from the fact that I use template-class definitions, I did not quite understand what is causing the problem when using templates and why it works when not using templates. Could someone please further clarify this?

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• Android JSon Array is not working with Maplocations class

  - by user1505962

  I am developing a map application in android i have made maplocation class to pass latitude and longitude and using Json Array to fetch data from MYSQl to display in map.But When I run application it crashed unfortunantely here is my log cat 07-07 14:02:26.423: E/AndroidRuntime(366): FATAL EXCEPTION: main 07-07 14:02:26.423: E/AndroidRuntime(366): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.icons.draw.view/com.icons.draw.view.DrawIcons}: android.view.InflateException: Binary XML file line #6: Error inflating class com.icons.draw.view.LocationViewers 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.os.Handler.dispatchMessage(Handler.java:99) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.os.Looper.loop(Looper.java:130) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread.main(ActivityThread.java:3683) 07-07 14:02:26.423: E/AndroidRuntime(366): at java.lang.reflect.Method.invokeNative(Native Method) 07-07 14:02:26.423: E/AndroidRuntime(366): at java.lang.reflect.Method.invoke(Method.java:507) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 07-07 14:02:26.423: E/AndroidRuntime(366): at dalvik.system.NativeStart.main(Native Method) 07-07 14:02:26.423: E/AndroidRuntime(366): Caused by: android.view.InflateException: Binary XML file line #6: Error inflating class com.icons.draw.view.LocationViewers 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.createView(LayoutInflater.java:518) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:570) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.rInflate(LayoutInflater.java:623) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.inflate(LayoutInflater.java:408) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.inflate(LayoutInflater.java:320) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.inflate(LayoutInflater.java:276) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:207) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.Activity.setContentView(Activity.java:1657) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.icons.draw.view.DrawIcons.onCreate(DrawIcons.java:16) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 07-07 14:02:26.423: E/AndroidRuntime(366): ... 11 more 07-07 14:02:26.423: E/AndroidRuntime(366): Caused by: java.lang.reflect.InvocationTargetException 07-07 14:02:26.423: E/AndroidRuntime(366): at java.lang.reflect.Constructor.constructNative(Native Method) 07-07 14:02:26.423: E/AndroidRuntime(366): at java.lang.reflect.Constructor.newInstance(Constructor.java:415) 07-07 14:02:26.423: E/AndroidRuntime(366): at android.view.LayoutInflater.createView(LayoutInflater.java:505) 07-07 14:02:26.423: E/AndroidRuntime(366): ... 21 more 07-07 14:02:26.423: E/AndroidRuntime(366): Caused by: java.lang.NullPointerException 07-07 14:02:26.423: E/AndroidRuntime(366): at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:112) 07-07 14:02:26.423: E/AndroidRuntime(366): at org.json.JSONTokener.nextValue(JSONTokener.java:90) 07-07 14:02:26.423: E/AndroidRuntime(366): at org.json.JSONArray.<init>(JSONArray.java:87) 07-07 14:02:26.423: E/AndroidRuntime(366): at org.json.JSONArray.<init>(JSONArray.java:103) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.icons.draw.view.LocationViewers.getMapLocations(LocationViewers.java:102) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.icons.draw.view.LocationViewers.init(LocationViewers.java:65) 07-07 14:02:26.423: E/AndroidRuntime(366): at com.icons.draw.view.LocationViewers.<init>(LocationViewers.java:45) 07-07 14:02:26.423: E/AndroidRuntime(366): ... 24 more And Here is My JSOn Array and loop code to make markers double LAT; double LANG; String INFO; public List<MapLocation> getMapLocations() { if (mapLocations == null) { try{ jArray = new JSONArray(result); JSONObject json_data=null; for(int i=0;i<jArray.length();i++){ json_data = jArray.getJSONObject(i); LAT=json_data.getDouble("lat"); LANG=json_data.getDouble("lang"); INFO=json_data.getString("info"); mapLocations = new ArrayList<MapLocation>(); mapLocations.add(new MapLocation(INFO,LAT,LANG)); } } catch(JSONException e1){ Toast.makeText(getContext(), "No Vehicles Found" ,Toast.LENGTH_LONG).show(); } catch (ParseException e1) { e1.printStackTrace(); } } return mapLocations; } Please Help to Remove this error

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• Reordering Variadic Parameters

  - by void-pointer

  I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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• Arduino: Putting servos in my class causes them to rotate all the way to one side

  - by user2526712

  I am trying to create a new class that controls two servos. My code compiles just fine. However, when I run it, the servos just turn all the way to one direction. This seems to happen when I try instantiating the class (when in the constructor, I attach the servos in the class to pins). In My class's header file, I have [UPDATED] #ifndef ServoController_h #define ServoController_h #include "Arduino.h" #include <Servo.h> class ServoController { public: ServoController(int rotateServoPin, int elevateServoPin); void rotate(int degrees); void elevate(int degrees); private: Servo rotateServo; Servo elevateServo; int elevationAngle; int azimuthAngle; }; #endif Code so far for my Class: #include "Arduino.h" #include "ServoController.h" ServoController::ServoController(int rotateServoPin, int elevateServoPin) { azimuthAngle = 0; elevationAngle = 0; elevateServo.attach(elevateServoPin); rotateServo.attach(rotateServoPin); } void ServoController::rotate(int degrees) { //TO DO rotateServo.write(degrees); } void ServoController::elevate(int degrees) { //TO DO elevateServo.write(degrees); } And finally my arduino sketch so far is just: #include <ServoController.h> #include <Servo.h> ServoController sc(2 , 3); void setup() { } void loop() { } I'm pretty sure the circuit I am using is fine, since if I do not use my class, and just use the servo library directly in my arduino file, the servos move correctly. any ideas why this might happen? [UPDATE] I actually got this working. In my constructor, I have removed the lines to attach the servos to pins. Instead, I have added another method to my class which does the attachment. ServoController::ServoController(int rotateServoPin, int elevateServoPin) { azimuthAngle = 0; elevationAngle = 0; // elevateServo.attach(elevateServoPin); // rotateServo.attach(rotateServoPin); } void ServoController::attachPins(int rotateServoPin, int elevateServoPin) { azimuthAngle = 0; elevationAngle = 0; elevateServo.attach(elevateServoPin); rotateServo.attach(rotateServoPin); } I then call this in my sketch's setup() function: void setup() { sc.attachPins(2,3); } It seems like if I attach my servos outside of the setup() function, my problem occurs. [UPDATE July 27 9:13PM] Verified something with another test: I created a new sketch where I attached a servo before setup(): #include <Servo.h> Servo servo0; servo0.attach(2); void setup() { } void loop() // this function runs repeatedly after setup() finishes { servo0.write(90); delay(2000); servo0.write(135); delay(2000); servo0.write(45); delay(2000); } When I try to compile, Arduino throws an error: "testservotest:4: error: expected constructor, destructor, or type conversion before '.' token" So there was an error, but it was not thrown when the attach method was called from a class Thanks very much

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• What is a good java data structure for storing nested items (like cities in states)?

  - by anotherAlan

  I'm just getting started in Java and am looking for advice on a good way to store nested sets of data. For example, I'm interested in storing city population data that can be accessed by looking up the city in a given state. (Note: eventually, other data will be stored with each city as well, this is just the first attempt at getting started.) The current approach I'm using is to have a StateList Object which contains a HashMap that stores State Objects via a string key (i.e. HashMap<String, State>). Each State Object contains its own HashMap of City Objects keyed off the city name (i.e. HashMap<String, City>). A cut down version of what I've come up with looks like this: // TestPopulation.java public class TestPopulation { public static void main(String [] args) { // build the stateList Object StateList sl = new StateList(); // get a test state State stateAl = sl.getState("AL"); // make sure it's there. if(stateAl != null) { // add a city stateAl.addCity("Abbeville"); // now grab the city City cityAbbevilleAl = stateAl.getCity("Abbeville"); cityAbbevilleAl.setPopulation(2987); System.out.print("The city has a pop of: "); System.out.println(Integer.toString(cityAbbevilleAl.getPopulation())); } // otherwise, print an error else { System.out.println("That was an invalid state"); } } } // StateList.java import java.util.*; public class StateList { // define hash map to hold the states private HashMap<String, State> theStates = new HashMap<String, State>(); // setup constructor that loads the states public StateList() { String[] stateCodes = {"AL","AK","AZ","AR","CA","CO"}; // etc... for (String s : stateCodes) { State newState = new State(s); theStates.put(s, newState); } } // define method for getting a state public State getState(String stateCode) { if(theStates.containsKey(stateCode)) { return theStates.get(stateCode); } else { return null; } } } // State.java import java.util.*; public class State { // Setup the state code String stateCode; // HashMap for cities HashMap<String, City> cities = new HashMap<String, City>(); // define the constructor public State(String newStateCode) { System.out.println("Creating State: " + newStateCode); stateCode = newStateCode; } // define the method for adding a city public void addCity(String newCityName) { City newCityObj = new City(newCityName); cities.put(newCityName, newCityObj); } // define the method for getting a city public City getCity(String cityName) { if(cities.containsKey(cityName)) { return cities.get(cityName); } else { return null; } } } // City.java public class City { // Define the instance vars String cityName; int cityPop; // setup the constructor public City(String newCityName) { cityName = newCityName; System.out.println("Created City: " + newCityName); } public void setPopulation(int newPop) { cityPop = newPop; } public int getPopulation() { return cityPop; } } This is working for me, but I'm wondering if there are gotchas that I haven't run into, or if there are alternate/better ways to do the same thing. (P.S. I know that I need to add some more error checking in, but right now, I'm focused on trying to figure out a good data structure.) (NOTE: Edited to change setPop() and getPop() to setPopulation() and getPopulation() respectively to avoid confucsion)

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• Demystifying Silverlight Dependency Properties

  - by dwahlin

  I have the opportunity to teach a lot of people about Silverlight (amongst other technologies) and one of the topics that definitely confuses people initially is the concept of dependency properties. I confess that when I first heard about them my initial thought was “Why do we need a specialized type of property?” While you can certainly use standard CLR properties in Silverlight applications, Silverlight relies heavily on dependency properties for just about everything it does behind the scenes. In fact, dependency properties are an essential part of the data binding, template, style and animation functionality available in Silverlight. They simply back standard CLR properties. In this post I wanted to put together a (hopefully) simple explanation of dependency properties and why you should care about them if you’re currently working with Silverlight or looking to move to it.   What are Dependency Properties? XAML provides a great way to define layout controls, user input controls, shapes, colors and data binding expressions in a declarative manner. There’s a lot that goes on behind the scenes in order to make XAML work and an important part of that magic is the use of dependency properties. If you want to bind data to a property, style it, animate it or transform it in XAML then the property involved has to be a dependency property to work properly. If you’ve ever positioned a control in a Canvas using Canvas.Left or placed a control in a specific Grid row using Grid.Row then you’ve used an attached property which is a specialized type of dependency property. Dependency properties play a key role in XAML and the overall Silverlight framework. Any property that you bind, style, template, animate or transform must be a dependency property in Silverlight applications. You can programmatically bind values to controls and work with standard CLR properties, but if you want to use the built-in binding expressions available in XAML (one of my favorite features) or the Binding class available through code then dependency properties are a necessity. Dependency properties aren’t needed in every situation, but if you want to customize your application very much you’ll eventually end up needing them. For example, if you create a custom user control and want to expose a property that consumers can use to change the background color, you have to define it as a dependency property if you want bindings, styles and other features to be available for use. Now that the overall purpose of dependency properties has been discussed let’s take a look at how you can create them. Creating Dependency Properties When .NET first came out you had to write backing fields for each property that you defined as shown next: Brush _ScheduleBackground; public Brush ScheduleBackground { get { return _ScheduleBackground; } set { _ScheduleBackground = value; } } Although .NET 2.0 added auto-implemented properties (for example: public Brush ScheduleBackground { get; set; }) where the compiler would automatically generate the backing field used by get and set blocks, the concept is still the same as shown in the above code; a property acts as a wrapper around a field. Silverlight dependency properties replace the _ScheduleBackground field shown in the previous code and act as the backing store for a standard CLR property. The following code shows an example of defining a dependency property named ScheduleBackgroundProperty: public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null);   Looking through the code the first thing that may stand out is that the definition for ScheduleBackgroundProperty is marked as static and readonly and that the property appears to be of type DependencyProperty. This is a standard pattern that you’ll use when working with dependency properties. You’ll also notice that the property explicitly adds the word “Property” to the name which is another standard you’ll see followed. In addition to defining the property, the code also makes a call to the static DependencyProperty.Register method and passes the name of the property to register (ScheduleBackground in this case) as a string. The type of the property, the type of the class that owns the property and a null value (more on the null value later) are also passed. In this example a class named Scheduler acts as the owner. The code handles registering the property as a dependency property with the call to Register(), but there’s a little more work that has to be done to allow a value to be assigned to and retrieved from the dependency property. The following code shows the complete code that you’ll typically use when creating a dependency property. You can find code snippets that greatly simplify the process of creating dependency properties out on the web. The MVVM Light download available from http://mvvmlight.codeplex.com comes with built-in dependency properties snippets as well. public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null); public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } The standard CLR property code shown above should look familiar since it simply wraps the dependency property. However, you’ll notice that the get and set blocks call GetValue and SetValue methods respectively to perform the appropriate operation on the dependency property. GetValue and SetValue are members of the DependencyObject class which is another key component of the Silverlight framework. Silverlight controls and classes (TextBox, UserControl, CompositeTransform, DataGrid, etc.) ultimately derive from DependencyObject in their inheritance hierarchy so that they can support dependency properties. Dependency properties defined in Silverlight controls and other classes tend to follow the pattern of registering the property by calling Register() and then wrapping the dependency property in a standard CLR property (as shown above). They have a standard property that wraps a registered dependency property and allows a value to be assigned and retrieved. If you need to expose a new property on a custom control that supports data binding expressions in XAML then you’ll follow this same pattern. Dependency properties are extremely useful once you understand why they’re needed and how they’re defined. Detecting Changes and Setting Defaults When working with dependency properties there will be times when you want to assign a default value or detect when a property changes so that you can keep the user interface in-sync with the property value. Silverlight’s DependencyProperty.Register() method provides a fourth parameter that accepts a PropertyMetadata object instance. PropertyMetadata can be used to hook a callback method to a dependency property. The callback method is called when the property value changes. PropertyMetadata can also be used to assign a default value to the dependency property. By assigning a value of null for the final parameter passed to Register() you’re telling the property that you don’t care about any changes and don’t have a default value to apply. Here are the different constructor overloads available on the PropertyMetadata class: PropertyMetadata Constructor Overload Description PropertyMetadata(Object) Used to assign a default value to a dependency property. PropertyMetadata(PropertyChangedCallback) Used to assign a property changed callback method. PropertyMetadata(Object, PropertyChangedCalback) Used to assign a default property value and a property changed callback.   There are many situations where you need to know when a dependency property changes or where you want to apply a default. Performing either task is easily accomplished by creating a new instance of the PropertyMetadata class and passing the appropriate values to its constructor. The following code shows an enhanced version of the initial dependency property code shown earlier that demonstrates these concepts: public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), new PropertyMetadata(new SolidColorBrush(Colors.LightGray), ScheduleBackgroundChanged)); private static void ScheduleBackgroundChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var scheduler = d as Scheduler; scheduler.Background = e.NewValue as Brush; } The code wires ScheduleBackgroundProperty to a property change callback method named ScheduleBackgroundChanged. What’s interesting is that this callback method is static (as is the dependency property) so it gets passed the instance of the object that owns the property that has changed (otherwise we wouldn’t be able to get to the object instance). In this example the dependency object is cast to a Scheduler object and its Background property is assigned to the new value of the dependency property. The code also handles assigning a default value of LightGray to the dependency property by creating a new instance of a SolidColorBrush. To Sum Up In this post you’ve seen the role of dependency properties and how they can be defined in code. They play a big role in XAML and the overall Silverlight framework. You can think of dependency properties as being replacements for fields that you’d normally use with standard CLR properties. In addition to a discussion on how dependency properties are created, you also saw how to use the PropertyMetadata class to define default dependency property values and hook a dependency property to a callback method. The most important thing to understand with dependency properties (especially if you’re new to Silverlight) is that they’re needed if you want a property to support data binding, animations, transformations and styles properly. Any time you create a property on a custom control or user control that has these types of requirements you’ll want to pick a dependency property over of a standard CLR property with a backing field. There’s more that can be covered with dependency properties including a related property called an attached property….more to come.

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• Metro: Promises

  - by Stephen.Walther

  The goal of this blog entry is to describe the Promise class in the WinJS library. You can use promises whenever you need to perform an asynchronous operation such as retrieving data from a remote website or a file from the file system. Promises are used extensively in the WinJS library. Asynchronous Programming Some code executes immediately, some code requires time to complete or might never complete at all. For example, retrieving the value of a local variable is an immediate operation. Retrieving data from a remote website takes longer or might not complete at all. When an operation might take a long time to complete, you should write your code so that it executes asynchronously. Instead of waiting for an operation to complete, you should start the operation and then do something else until you receive a signal that the operation is complete. An analogy. Some telephone customer service lines require you to wait on hold – listening to really bad music – until a customer service representative is available. This is synchronous programming and very wasteful of your time. Some newer customer service lines enable you to enter your telephone number so the customer service representative can call you back when a customer representative becomes available. This approach is much less wasteful of your time because you can do useful things while waiting for the callback. There are several patterns that you can use to write code which executes asynchronously. The most popular pattern in JavaScript is the callback pattern. When you call a function which might take a long time to return a result, you pass a callback function to the function. For example, the following code (which uses jQuery) includes a function named getFlickrPhotos which returns photos from the Flickr website which match a set of tags (such as “dog” and “funny”): function getFlickrPhotos(tags, callback) { $.getJSON( "http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?", { tags: tags, tagmode: "all", format: "json" }, function (data) { if (callback) { callback(data.items); } } ); } getFlickrPhotos("funny, dogs", function(data) { $.each(data, function(index, item) { console.log(item); }); }); The getFlickr() function includes a callback parameter. When you call the getFlickr() function, you pass a function to the callback parameter which gets executed when the getFlicker() function finishes retrieving the list of photos from the Flickr web service. In the code above, the callback function simply iterates through the results and writes each result to the console. Using callbacks is a natural way to perform asynchronous programming with JavaScript. Instead of waiting for an operation to complete, sitting there and listening to really bad music, you can get a callback when the operation is complete. Using Promises The CommonJS website defines a promise like this (http://wiki.commonjs.org/wiki/Promises): “Promises provide a well-defined interface for interacting with an object that represents the result of an action that is performed asynchronously, and may or may not be finished at any given point in time. By utilizing a standard interface, different components can return promises for asynchronous actions and consumers can utilize the promises in a predictable manner.” A promise provides a standard pattern for specifying callbacks. In the WinJS library, when you create a promise, you can specify three callbacks: a complete callback, a failure callback, and a progress callback. Promises are used extensively in the WinJS library. The methods in the animation library, the control library, and the binding library all use promises. For example, the xhr() method included in the WinJS base library returns a promise. The xhr() method wraps calls to the standard XmlHttpRequest object in a promise. The following code illustrates how you can use the xhr() method to perform an Ajax request which retrieves a file named Photos.txt: var options = { url: "/data/photos.txt" }; WinJS.xhr(options).then( function (xmlHttpRequest) { console.log("success"); var data = JSON.parse(xmlHttpRequest.responseText); console.log(data); }, function(xmlHttpRequest) { console.log("fail"); }, function(xmlHttpRequest) { console.log("progress"); } ) The WinJS.xhr() method returns a promise. The Promise class includes a then() method which accepts three callback functions: a complete callback, an error callback, and a progress callback: Promise.then(completeCallback, errorCallback, progressCallback) In the code above, three anonymous functions are passed to the then() method. The three callbacks simply write a message to the JavaScript Console. The complete callback also dumps all of the data retrieved from the photos.txt file. Creating Promises You can create your own promises by creating a new instance of the Promise class. The constructor for the Promise class requires a function which accepts three parameters: a complete, error, and progress function parameter. For example, the code below illustrates how you can create a method named wait10Seconds() which returns a promise. The progress function is called every second and the complete function is not called until 10 seconds have passed: (function () { "use strict"; var app = WinJS.Application; function wait10Seconds() { return new WinJS.Promise(function (complete, error, progress) { var seconds = 0; var intervalId = window.setInterval(function () { seconds++; progress(seconds); if (seconds > 9) { window.clearInterval(intervalId); complete(); } }, 1000); }); } app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { wait10Seconds().then( function () { console.log("complete") }, function () { console.log("error") }, function (seconds) { console.log("progress:" + seconds) } ); } } app.start(); })(); All of the work happens in the constructor function for the promise. The window.setInterval() method is used to execute code every second. Every second, the progress() callback method is called. If more than 10 seconds have passed then the complete() callback method is called and the clearInterval() method is called. When you execute the code above, you can see the output in the Visual Studio JavaScript Console. Creating a Timeout Promise In the previous section, we created a custom Promise which uses the window.setInterval() method to complete the promise after 10 seconds. We really did not need to create a custom promise because the Promise class already includes a static method for returning promises which complete after a certain interval. The code below illustrates how you can use the timeout() method. The timeout() method returns a promise which completes after a certain number of milliseconds. WinJS.Promise.timeout(3000).then( function(){console.log("complete")}, function(){console.log("error")}, function(){console.log("progress")} ); In the code above, the Promise completes after 3 seconds (3000 milliseconds). The Promise returned by the timeout() method does not support progress events. Therefore, the only message written to the console is the message “complete” after 10 seconds. Canceling Promises Some promises, but not all, support cancellation. When you cancel a promise, the promise’s error callback is executed. For example, the following code uses the WinJS.xhr() method to perform an Ajax request. However, immediately after the Ajax request is made, the request is cancelled. // Specify Ajax request options var options = { url: "/data/photos.txt" }; // Make the Ajax request var request = WinJS.xhr(options).then( function (xmlHttpRequest) { console.log("success"); }, function (xmlHttpRequest) { console.log("fail"); }, function (xmlHttpRequest) { console.log("progress"); } ); // Cancel the Ajax request request.cancel(); When you run the code above, the message “fail” is written to the Visual Studio JavaScript Console. Composing Promises You can build promises out of other promises. In other words, you can compose promises. There are two static methods of the Promise class which you can use to compose promises: the join() method and the any() method. When you join promises, a promise is complete when all of the joined promises are complete. When you use the any() method, a promise is complete when any of the promises complete. The following code illustrates how to use the join() method. A new promise is created out of two timeout promises. The new promise does not complete until both of the timeout promises complete: WinJS.Promise.join([WinJS.Promise.timeout(1000), WinJS.Promise.timeout(5000)]) .then(function () { console.log("complete"); }); The message “complete” will not be written to the JavaScript Console until both promises passed to the join() method completes. The message won’t be written for 5 seconds (5,000 milliseconds). The any() method completes when any promise passed to the any() method completes: WinJS.Promise.any([WinJS.Promise.timeout(1000), WinJS.Promise.timeout(5000)]) .then(function () { console.log("complete"); }); The code above writes the message “complete” to the JavaScript Console after 1 second (1,000 milliseconds). The message is written to the JavaScript console immediately after the first promise completes and before the second promise completes. Summary The goal of this blog entry was to describe WinJS promises. First, we discussed how promises enable you to easily write code which performs asynchronous actions. You learned how to use a promise when performing an Ajax request. Next, we discussed how you can create your own promises. You learned how to create a new promise by creating a constructor function with complete, error, and progress parameters. Finally, you learned about several advanced methods of promises. You learned how to use the timeout() method to create promises which complete after an interval of time. You also learned how to cancel promises and compose promises from other promises.

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• WPF Login Verification Using Active Directory

  - by psheriff

  Back in October of 2009 I created a WPF login screen (Figure 1) that just showed how to create the layout for a login screen. That one sample is probably the most downloaded sample we have. So in this blog post, I thought I would update that screen and also hook it up to show how to authenticate your user against Active Directory. Figure 1: Original WPF Login Screen I have updated not only the code behind for this login screen, but also the look and feel as shown in Figure 2. Figure 2: An Updated WPF Login Screen The UI To create the UI for this login screen you can refer to my October of 2009 blog post to see how to create the borderless window. You can then look at the sample code to see how I created the linear gradient brush for the background. There are just a few differences in this screen compared to the old version. First, I changed the key image and instead of using words for the Cancel and Login buttons, I used some icons. Secondly I added a text box to hold the Domain name that you wish to authenticate against. This text box is automatically filled in if you are connected to a network. In the Window_Loaded event procedure of the winLogin window you can retrieve the user’s domain name from the Environment.UserDomainName property. For example: txtDomain.Text = Environment.UserDomainName The ADHelper Class Instead of coding the call to authenticate the user directly in the login screen I created an ADHelper class. This will make it easier if you want to add additional AD calls in the future. The ADHelper class contains just one method at this time called AuthenticateUser. This method authenticates a user name and password against the specified domain. The login screen will gather the credentials from the user such as their user name and password, and also the domain name to authenticate against. To use this ADHelper class you will need to add a reference to the System.DirectoryServices.dll in .NET. The AuthenticateUser Method In order to authenticate a user against your Active Directory you will need to supply a valid LDAP path string to the constructor of the DirectoryEntry class. The LDAP path string will be in the format LDAP://DomainName. You will also pass in the user name and password to the constructor of the DirectoryEntry class as well. With a DirectoryEntry object populated with this LDAP path string, the user name and password you will now pass this object to the constructor of a DirectorySearcher object. You then perform the FindOne method on the DirectorySearcher object. If the DirectorySearcher object returns a SearchResult then the credentials supplied are valid. If the credentials are not valid on the Active Directory then an exception is thrown. C#public bool AuthenticateUser(string domainName, string userName,  string password){  bool ret = false;   try  {    DirectoryEntry de = new DirectoryEntry("LDAP://" + domainName,                                           userName, password);    DirectorySearcher dsearch = new DirectorySearcher(de);    SearchResult results = null;     results = dsearch.FindOne();     ret = true;  }  catch  {    ret = false;  }   return ret;} Visual Basic Public Function AuthenticateUser(ByVal domainName As String, _ ByVal userName As String, ByVal password As String) As Boolean  Dim ret As Boolean = False   Try    Dim de As New DirectoryEntry("LDAP://" & domainName, _                                 userName, password)    Dim dsearch As New DirectorySearcher(de)    Dim results As SearchResult = Nothing     results = dsearch.FindOne()     ret = True  Catch    ret = False  End Try   Return retEnd Function In the Click event procedure under the Login button you will find the following code that will validate the credentials that the user types into the login window. C#private void btnLogin_Click(object sender, RoutedEventArgs e){  ADHelper ad = new ADHelper();   if(ad.AuthenticateUser(txtDomain.Text,         txtUserName.Text, txtPassword.Password))    DialogResult = true;  else    MessageBox.Show("Unable to Authenticate Using the                      Supplied Credentials");} Visual BasicPrivate Sub btnLogin_Click(ByVal sender As Object, _ ByVal e As RoutedEventArgs)  Dim ad As New ADHelper()   If ad.AuthenticateUser(txtDomain.Text, txtUserName.Text, _                         txtPassword.Password) Then    DialogResult = True  Else    MessageBox.Show("Unable to Authenticate Using the                      Supplied Credentials")  End IfEnd Sub Displaying the Login Screen At some point when your application launches, you will need to display your login screen modally. Below is the code that you would call to display the login form (named winLogin in my sample application). This code is called from the main application form, and thus the owner of the login screen is set to “this”. You then call the ShowDialog method on the login screen to have this form displayed modally. After the user clicks on one of the two buttons you need to check to see what the DialogResult property was set to. The DialogResult property is a nullable type and thus you first need to check to see if the value has been set. C# private void DisplayLoginScreen(){  winLogin win = new winLogin();   win.Owner = this;  win.ShowDialog();  if (win.DialogResult.HasValue && win.DialogResult.Value)    MessageBox.Show("User Logged In");  else    this.Close();} Visual Basic Private Sub DisplayLoginScreen()  Dim win As New winLogin()   win.Owner = Me  win.ShowDialog()  If win.DialogResult.HasValue And win.DialogResult.Value Then    MessageBox.Show("User Logged In")  Else    Me.Close()  End IfEnd Sub Summary Creating a nice looking login screen is fairly simple to do in WPF. Using the Active Directory services from a WPF application should make your desktop programming task easier as you do not need to create your own user authentication system. I hope this article gave you some ideas on how to create a login screen in WPF. NOTE: You can download the complete sample code for this blog entry at my website: http://www.pdsa.com/downloads. Click on Tips & Tricks, then select 'WPF Login Verification Using Active Directory' from the drop down list. Good Luck with your Coding,Paul Sheriff ** SPECIAL OFFER FOR MY BLOG READERS **We frequently offer a FREE gift for readers of my blog. Visit http://www.pdsa.com/Event/Blog for your FREE gift!

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• Windows Phone 7 : Dragging and flicking UI controls

  - by TechTwaddle

  Who would want to flick and drag UI controls!? There might not be many use cases but I think some concepts here are worthy of a post. So we will create a simple silverlight application for windows phone 7, containing a canvas element on which we’ll place a button control and an image and then, as the title says, drag and flick the controls. Here’s Mainpage.xaml, <Grid x:Name="LayoutRoot" Background="Transparent">   <Grid.RowDefinitions>     <RowDefinition Height="Auto"/>     <RowDefinition Height="*"/>   </Grid.RowDefinitions>     <!--TitlePanel contains the name of the application and page title-->   <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">     <TextBlock x:Name="ApplicationTitle" Text="KINETICS" Style="{StaticResource PhoneTextNormalStyle}"/>     <TextBlock x:Name="PageTitle" Text="drag and flick" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>   </StackPanel>     <!--ContentPanel - place additional content here-->   <Grid x:Name="ContentPanel" Grid.Row="1" >     <Canvas x:Name="MainCanvas" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">       <Canvas.Background>         <LinearGradientBrush StartPoint="0 0" EndPoint="0 1">           <GradientStop Offset="0" Color="Black"/>           <GradientStop Offset="1.5" Color="BlanchedAlmond"/>         </LinearGradientBrush>       </Canvas.Background>     </Canvas>   </Grid> </Grid> the second row in the main grid contains a canvas element, MainCanvas, with its horizontal and vertical alignment set to stretch so that it occupies the entire grid. The canvas background is a linear gradient brush starting with Black and ending with BlanchedAlmond. We’ll add the button and image control to this canvas at run time. Moving to Mainpage.xaml.cs the Mainpage class contains the following members, public partial class MainPage : PhoneApplicationPage {     Button FlickButton;     Image FlickImage;       FrameworkElement ElemToMove = null;     double ElemVelX, ElemVelY;       const double SPEED_FACTOR = 60;       DispatcherTimer timer; FlickButton and FlickImage are the controls that we’ll add to the canvas. ElemToMove, ElemVelX and ElemVelY will be used by the timer callback to move the ui control. SPEED_FACTOR is used to scale the velocities of ui controls. Here’s the Mainpage constructor, // Constructor public MainPage() {     InitializeComponent();       AddButtonToCanvas();       AddImageToCanvas();       timer = new DispatcherTimer();     timer.Interval = TimeSpan.FromMilliseconds(35);     timer.Tick += new EventHandler(OnTimerTick); } We’ll look at those AddButton and AddImage functions in a moment. The constructor initializes a timer which fires every 35 milliseconds, this timer will be started after the flick gesture completes with some inertia. Back to AddButton and AddImage functions, void AddButtonToCanvas() {     LinearGradientBrush brush;     GradientStop stop1, stop2;       Random rand = new Random(DateTime.Now.Millisecond);       FlickButton = new Button();     FlickButton.Content = "";     FlickButton.Width = 100;     FlickButton.Height = 100;       brush = new LinearGradientBrush();     brush.StartPoint = new Point(0, 0);     brush.EndPoint = new Point(0, 1);       stop1 = new GradientStop();     stop1.Offset = 0;     stop1.Color = Colors.White;       stop2 = new GradientStop();     stop2.Offset = 1;     stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color;       brush.GradientStops.Add(stop1);     brush.GradientStops.Add(stop2);       FlickButton.Background = brush;       Canvas.SetTop(FlickButton, rand.Next(0, 400));     Canvas.SetLeft(FlickButton, rand.Next(0, 200));       MainCanvas.Children.Add(FlickButton);       //subscribe to events     FlickButton.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);     FlickButton.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted); } this function is basically glorifying a simple task. After creating the button and setting its height and width, its background is set to a linear gradient brush. The direction of the gradient is from top towards bottom and notice that the second stop color is the PhoneAccentColor, which changes along with the theme of the device. The line,     stop2.Color = (Application.Current.Resources["PhoneAccentBrush"] as SolidColorBrush).Color; does the magic of extracting the PhoneAccentBrush from application’s resources, getting its color and assigning it to the gradient stop. AddImage function is straight forward in comparison, void AddImageToCanvas() {     Random rand = new Random(DateTime.Now.Millisecond);       FlickImage = new Image();     FlickImage.Source = new BitmapImage(new Uri("/images/Marble.png", UriKind.Relative));       Canvas.SetTop(FlickImage, rand.Next(0, 400));     Canvas.SetLeft(FlickImage, rand.Next(0, 200));       MainCanvas.Children.Add(FlickImage);       //subscribe to events     FlickImage.ManipulationDelta += new EventHandler<ManipulationDeltaEventArgs>(OnManipulationDelta);     FlickImage.ManipulationCompleted += new EventHandler<ManipulationCompletedEventArgs>(OnManipulationCompleted); } The ManipulationDelta and ManipulationCompleted handlers are same for both the button and the image. OnManipulationDelta() should look familiar, a similar implementation was used in the previous post, void OnManipulationDelta(object sender, ManipulationDeltaEventArgs args) {     FrameworkElement Elem = sender as FrameworkElement;       double Left = Canvas.GetLeft(Elem);     double Top = Canvas.GetTop(Elem);       Left += args.DeltaManipulation.Translation.X;     Top += args.DeltaManipulation.Translation.Y;       //check for bounds     if (Left < 0)     {         Left = 0;     }     else if (Left > (MainCanvas.ActualWidth - Elem.ActualWidth))     {         Left = MainCanvas.ActualWidth - Elem.ActualWidth;     }       if (Top < 0)     {         Top = 0;     }     else if (Top > (MainCanvas.ActualHeight - Elem.ActualHeight))     {         Top = MainCanvas.ActualHeight - Elem.ActualHeight;     }       Canvas.SetLeft(Elem, Left);     Canvas.SetTop(Elem, Top); } all it does is calculate the control’s position, check for bounds and then set the top and left of the control. OnManipulationCompleted() is more interesting because here we need to check if the gesture completed with any inertia and if it did, start the timer and continue to move the ui control until it comes to a halt slowly, void OnManipulationCompleted(object sender, ManipulationCompletedEventArgs args) {     FrameworkElement Elem = sender as FrameworkElement;       if (args.IsInertial)     {         ElemToMove = Elem;           Debug.WriteLine("Linear VelX:{0:0.00}  VelY:{1:0.00}", args.FinalVelocities.LinearVelocity.X,             args.FinalVelocities.LinearVelocity.Y);           ElemVelX = args.FinalVelocities.LinearVelocity.X / SPEED_FACTOR;         ElemVelY = args.FinalVelocities.LinearVelocity.Y / SPEED_FACTOR;           timer.Start();     } } ManipulationCompletedEventArgs contains a member, IsInertial, which is set to true if the manipulation was completed with some inertia. args.FinalVelocities.LinearVelocity.X and .Y will contain the velocities along the X and Y axis. We need to scale down these values so they can be used to increment the ui control’s position sensibly. A reference to the ui control is stored in ElemToMove and the velocities are stored as well, these will be used in the timer callback to access the ui control. And finally, we start the timer. The timer callback function is as follows, void OnTimerTick(object sender, EventArgs e) {     if (null != ElemToMove)     {         double Left, Top;         Left = Canvas.GetLeft(ElemToMove);         Top = Canvas.GetTop(ElemToMove);           Left += ElemVelX;         Top += ElemVelY;           //check for bounds         if (Left < 0)         {             Left = 0;             ElemVelX *= -1;         }         else if (Left > (MainCanvas.ActualWidth - ElemToMove.ActualWidth))         {             Left = MainCanvas.ActualWidth - ElemToMove.ActualWidth;             ElemVelX *= -1;         }           if (Top < 0)         {             Top = 0;             ElemVelY *= -1;         }         else if (Top > (MainCanvas.ActualHeight - ElemToMove.ActualHeight))         {             Top = MainCanvas.ActualHeight - ElemToMove.ActualHeight;             ElemVelY *= -1;         }           Canvas.SetLeft(ElemToMove, Left);         Canvas.SetTop(ElemToMove, Top);           //reduce x,y velocities gradually         ElemVelX *= 0.9;         ElemVelY *= 0.9;           //when velocities become too low, break         if (Math.Abs(ElemVelX) < 1.0 && Math.Abs(ElemVelY) < 1.0)         {             timer.Stop();             ElemToMove = null;         }     } } if ElemToMove is not null, we get the top and left values of the control and increment the values with their X and Y velocities. Check for bounds, and if the control goes out of bounds we reverse its velocity. Towards the end, the velocities are reduced by 10% every time the timer callback is called, and if the velocities reach too low values the timer is stopped and ElemToMove is made null. Here’s a short video of the program, the video is a little dodgy because my display driver refuses to run the animations smoothly. The flicks aren’t always recognised but the program should run well on an actual device (or a pc with better configuration), You can download the source code from here: ButtonDragAndFlick.zip

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• Conway's Game of Life - C++ and Qt

  - by Jeff Bridge

  I've done all of the layouts and have most of the code written even. But, I'm stuck in two places. 1) I'm not quite sure how to set up the timer. Am I using it correctly in the gridwindow class? And, am I used the timer functions/signals/slots correctly with the other gridwindow functions. 2) In GridWindow's timerFired() function, I'm having trouble checking/creating the vector-vectors. I wrote out in the comments in that function exactly what I am trying to do. Any help would be much appreciated. main.cpp // Main file for running the grid window application. #include <QApplication> #include "gridwindow.h" //#include "timerwindow.h" #include <stdexcept> #include <string> #include <fstream> #include <sstream> #include <iostream> void Welcome(); // Welcome Function - Prints upon running program; outputs program name, student name/id, class section. void Rules(); // Rules Function: Prints the rules for Conway's Game of Life. using namespace std; // A simple main method to create the window class and then pop it up on the screen. int main(int argc, char *argv[]) { Welcome(); // Calls Welcome function to print student/assignment info. Rules(); // Prints Conway's Game Rules. QApplication app(argc, argv); // Creates the overall windowed application. int rows = 25, cols = 35; //The number of rows & columns in the game grid. GridWindow widget(NULL,rows,cols); // Creates the actual window (for the grid). widget.show(); // Shows the window on the screen. return app.exec(); // Goes into visual loop; starts executing GUI. } // Welcome Function: Prints my name/id, my class number, the assignment, and the program name. void Welcome() { cout << endl; cout << "-------------------------------------------------------------------------------------------------" << endl; cout << "Name/ID - Gabe Audick #7681539807" << endl; cout << "Class/Assignment - CSCI-102 Disccusion 29915: Homework Assignment #4" << endl; cout << "-------------------------------------------------------------------------------------------------" << endl << endl; } // Rules Function: Prints the rules for Conway's Game of Life. void Rules() { cout << "Welcome to Conway's Game of Life." << endl; cout << "Game Rules:" << endl; cout << "\t 1) Any living cell with fewer than two living neighbours dies, as if caused by underpopulation." << endl; cout << "\t 2) Any live cell with more than three live neighbours dies, as if by overcrowding." << endl; cout << "\t 3) Any live cell with two or three live neighbours lives on to the next generation." << endl; cout << "\t 4) Any dead cell with exactly three live neighbours becomes a live cell." << endl << endl; cout << "Enjoy." << endl << endl; } gridcell.h // A header file for a class representing a single cell in a grid of cells. #ifndef GRIDCELL_H_ #define GRIDCELL_H_ #include <QPalette> #include <QColor> #include <QPushButton> #include <Qt> #include <QWidget> #include <QFrame> #include <QHBoxLayout> #include <iostream> // An enum representing the two different states a cell can have. enum CellType { DEAD, // DEAD = Dead Cell. --> Color = White. LIVE // LIVE = Living Cell. ---> Color = White. }; /* Class: GridCell. A class representing a single cell in a grid. Each cell is implemented as a QT QFrame that contains a single QPushButton. The button is sized so that it takes up the entire frame. Each cell also keeps track of what type of cell it is based on the CellType enum. */ class GridCell : public QFrame { Q_OBJECT // Macro allowing us to have signals & slots on this object. private: QPushButton* button; // The button inside the cell that gives its clickability. CellType type; // The type of cell (DEAD or LIVE.) public slots: void handleClick(); // Callback for handling a click on the current cell. void setType(CellType type); // Cell type mutator. Calls the "redrawCell" function. signals: void typeChanged(CellType type); // Signal to notify listeners when the cell type has changed. public: GridCell(QWidget *parent = NULL); // Constructor for creating a cell. Takes parent widget or default parent to NULL. virtual ~GridCell(); // Destructor. void redrawCell(); // Redraws cell: Sets new type/color. CellType getType() const; //Simple getter for the cell type. private: Qt::GlobalColor getColorForCellType(); // Helper method. Returns color that cell should be based from its value. }; #endif gridcell.cpp #include <iostream> #include "gridcell.h" #include "utility.h" using namespace std; // Constructor: Creates a grid cell. GridCell::GridCell(QWidget *parent) : QFrame(parent) { this->type = DEAD; // Default: Cell is DEAD (white). setFrameStyle(QFrame::Box); // Set the frame style. This is what gives each box its black border. this->button = new QPushButton(this); //Creates button that fills entirety of each grid cell. this->button->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); // Expands button to fill space. this->button->setMinimumSize(19,19); //width,height // Min height and width of button. QHBoxLayout *layout = new QHBoxLayout(); //Creates a simple layout to hold our button and add the button to it. layout->addWidget(this->button); setLayout(layout); layout->setStretchFactor(this->button,1); // Lets the buttons expand all the way to the edges of the current frame with no space leftover layout->setContentsMargins(0,0,0,0); layout->setSpacing(0); connect(this->button,SIGNAL(clicked()),this,SLOT(handleClick())); // Connects clicked signal with handleClick slot. redrawCell(); // Calls function to redraw (set new type for) the cell. } // Basic destructor. GridCell::~GridCell() { delete this->button; } // Accessor for the cell type. CellType GridCell::getType() const { return(this->type); } // Mutator for the cell type. Also has the side effect of causing the cell to be redrawn on the GUI. void GridCell::setType(CellType type) { this->type = type; redrawCell(); } // Handler slot for button clicks. This method is called whenever the user clicks on this cell in the grid. void GridCell::handleClick() { // When clicked on... if(this->type == DEAD) // If type is DEAD (white), change to LIVE (black). type = LIVE; else type = DEAD; // If type is LIVE (black), change to DEAD (white). setType(type); // Sets new type (color). setType Calls redrawCell() to recolor. } // Method to check cell type and return the color of that type. Qt::GlobalColor GridCell::getColorForCellType() { switch(this->type) { default: case DEAD: return Qt::white; case LIVE: return Qt::black; } } // Helper method. Forces current cell to be redrawn on the GUI. Called whenever the setType method is invoked. void GridCell::redrawCell() { Qt::GlobalColor gc = getColorForCellType(); //Find out what color this cell should be. this->button->setPalette(QPalette(gc,gc)); //Force the button in the cell to be the proper color. this->button->setAutoFillBackground(true); this->button->setFlat(true); //Force QT to NOT draw the borders on the button } gridwindow.h // A header file for a QT window that holds a grid of cells. #ifndef GRIDWINDOW_H_ #define GRIDWINDOW_H_ #include <vector> #include <QWidget> #include <QTimer> #include <QGridLayout> #include <QLabel> #include <QApplication> #include "gridcell.h" /* class GridWindow: This is the class representing the whole window that comes up when this program runs. It contains a header section with a title, a middle section of MxN cells and a bottom section with buttons. */ class GridWindow : public QWidget { Q_OBJECT // Macro to allow this object to have signals & slots. private: std::vector<std::vector<GridCell*> > cells; // A 2D vector containing pointers to all the cells in the grid. QLabel *title; // A pointer to the Title text on the window. QTimer *timer; // Creates timer object. public slots: void handleClear(); // Handler function for clicking the Clear button. void handleStart(); // Handler function for clicking the Start button. void handlePause(); // Handler function for clicking the Pause button. void timerFired(); // Method called whenever timer fires. public: GridWindow(QWidget *parent = NULL,int rows=3,int cols=3); // Constructor. virtual ~GridWindow(); // Destructor. std::vector<std::vector<GridCell*> >& getCells(); // Accessor for the array of grid cells. private: QHBoxLayout* setupHeader(); // Helper function to construct the GUI header. QGridLayout* setupGrid(int rows,int cols); // Helper function to constructor the GUI's grid. QHBoxLayout* setupButtonRow(); // Helper function to setup the row of buttons at the bottom. }; #endif gridwindow.cpp #include <iostream> #include "gridwindow.h" using namespace std; // Constructor for window. It constructs the three portions of the GUI and lays them out vertically. GridWindow::GridWindow(QWidget *parent,int rows,int cols) : QWidget(parent) { QHBoxLayout *header = setupHeader(); // Setup the title at the top. QGridLayout *grid = setupGrid(rows,cols); // Setup the grid of colored cells in the middle. QHBoxLayout *buttonRow = setupButtonRow(); // Setup the row of buttons across the bottom. QVBoxLayout *layout = new QVBoxLayout(); // Puts everything together. layout->addLayout(header); layout->addLayout(grid); layout->addLayout(buttonRow); setLayout(layout); } // Destructor. GridWindow::~GridWindow() { delete title; } // Builds header section of the GUI. QHBoxLayout* GridWindow::setupHeader() { QHBoxLayout *header = new QHBoxLayout(); // Creates horizontal box. header->setAlignment(Qt::AlignHCenter); this->title = new QLabel("CONWAY'S GAME OF LIFE",this); // Creates big, bold, centered label (title): "Conway's Game of Life." this->title->setAlignment(Qt::AlignHCenter); this->title->setFont(QFont("Arial", 32, QFont::Bold)); header->addWidget(this->title); // Adds widget to layout. return header; // Returns header to grid window. } // Builds the grid of cells. This method populates the grid's 2D array of GridCells with MxN cells. QGridLayout* GridWindow::setupGrid(int rows,int cols) { QGridLayout *grid = new QGridLayout(); // Creates grid layout. grid->setHorizontalSpacing(0); // No empty spaces. Cells should be contiguous. grid->setVerticalSpacing(0); grid->setSpacing(0); grid->setAlignment(Qt::AlignHCenter); for(int i=0; i < rows; i++) //Each row is a vector of grid cells. { std::vector<GridCell*> row; // Creates new vector for current row. cells.push_back(row); for(int j=0; j < cols; j++) { GridCell *cell = new GridCell(); // Creates and adds new cell to row. cells.at(i).push_back(cell); grid->addWidget(cell,i,j); // Adds to cell to grid layout. Column expands vertically. grid->setColumnStretch(j,1); } grid->setRowStretch(i,1); // Sets row expansion horizontally. } return grid; // Returns grid. } // Builds footer section of the GUI. QHBoxLayout* GridWindow::setupButtonRow() { QHBoxLayout *buttonRow = new QHBoxLayout(); // Creates horizontal box for buttons. buttonRow->setAlignment(Qt::AlignHCenter); // Clear Button - Clears cell; sets them all to DEAD/white. QPushButton *clearButton = new QPushButton("CLEAR"); clearButton->setFixedSize(100,25); connect(clearButton, SIGNAL(clicked()), this, SLOT(handleClear())); buttonRow->addWidget(clearButton); // Start Button - Starts game when user clicks. Or, resumes game after being paused. QPushButton *startButton = new QPushButton("START/RESUME"); startButton->setFixedSize(100,25); connect(startButton, SIGNAL(clicked()), this, SLOT(handleStart())); buttonRow->addWidget(startButton); // Pause Button - Pauses simulation of game. QPushButton *pauseButton = new QPushButton("PAUSE"); pauseButton->setFixedSize(100,25); connect(pauseButton, SIGNAL(clicked()), this, SLOT(handlePause())); buttonRow->addWidget(pauseButton); // Quit Button - Exits program. QPushButton *quitButton = new QPushButton("EXIT"); quitButton->setFixedSize(100,25); connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit())); buttonRow->addWidget(quitButton); return buttonRow; // Returns bottom of layout. } /* SLOT method for handling clicks on the "clear" button. Receives "clicked" signals on the "Clear" button and sets all cells to DEAD. */ void GridWindow::handleClear() { for(unsigned int row=0; row < cells.size(); row++) // Loops through current rows' cells. { for(unsigned int col=0; col < cells[row].size(); col++) { GridCell *cell = cells[row][col]; // Grab the current cell & set its value to dead. cell->setType(DEAD); } } } /* SLOT method for handling clicks on the "start" button. Receives "clicked" signals on the "start" button and begins game simulation. */ void GridWindow::handleStart() { this->timer = new QTimer(this); // Creates new timer. connect(this->timer, SIGNAL(timeout()), this, SLOT(timerFired())); // Connect "timerFired" method class to the "timeout" signal fired by the timer. this->timer->start(500); // Timer to fire every 500 milliseconds. } /* SLOT method for handling clicks on the "pause" button. Receives "clicked" signals on the "pause" button and stops the game simulation. */ void GridWindow::handlePause() { this->timer->stop(); // Stops the timer. delete this->timer; // Deletes timer. } // Accessor method - Gets the 2D vector of grid cells. std::vector<std::vector<GridCell*> >& GridWindow::getCells() { return this->cells; } void GridWindow::timerFired() { // I'm not sure how to write this code. // I want to take the original vector-vector, and also make a new, empty vector-vector of the same size. // I would then go through the code below with the original vector, and apply the rules to the new vector-vector. // Finally, I would make the new vector-vecotr the original vector-vector. (That would be one step in the simulation.) cout << cells[1][2]; /* for (unsigned int m = 0; m < original.size(); m++) { for (unsigned int n = 0; n < original.at(m).size(); n++) { unsigned int neighbors = 0; //Begin counting number of neighbors. if (original[m-1][n-1].getType() == LIVE) // If a cell next to [i][j] is LIVE, add one to the neighbor count. neighbors += 1; if (original[m-1][n].getType() == LIVE) neighbors += 1; if (original[m-1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n-1].getType() == LIVE) neighbors += 1; if (original[m][n+1].getType() == LIVE) neighbors += 1; if (original[m+1][n-1].getType() == LIVE) neighbors += 1; if (original[m+1][n].getType() == LIVE) neighbors += 1; if (original[m+1][n+1].getType() == LIVE) neighbors += 1; if (original[m][n].getType() == LIVE && neighbors < 2) // Apply game rules to cells: Create new, updated grid with the roundtwo vector. roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == LIVE && neighbors > 3) roundtwo[m][n].setType(DEAD); else if (original[m][n].getType() == LIVE && (neighbors == 2 || neighbors == 3)) roundtwo[m][n].setType(LIVE); else if (original[m][n].getType() == DEAD && neighbors == 3) roundtwo[m][n].setType(LIVE); } }*/ }

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• concurrency::accelerator_view

  - by Daniel Moth

  Overview We saw previously that accelerator represents a target for our C++ AMP computation or memory allocation and that there is a notion of a default accelerator. We ended that post by introducing how one can obtain accelerator_view objects from an accelerator object through the accelerator class's default_view property and the create_view method. The accelerator_view objects can be thought of as handles to an accelerator. You can also construct an accelerator_view given another accelerator_view (through the copy constructor or the assignment operator overload). Speaking of operator overloading, you can also compare (for equality and inequality) two accelerator_view objects between them to determine if they refer to the same underlying accelerator. We'll see later that when we use concurrency::array objects, the allocation of data takes place on an accelerator at array construction time, so there is a constructor overload that accepts an accelerator_view object. We'll also see later that a new concurrency::parallel_for_each function overload can take an accelerator_view object, so it knows on what target to execute the computation (represented by a lambda that the parallel_for_each also accepts). Beyond normal usage, accelerator_view is a quality of service concept that offers isolation to multiple "consumers" of an accelerator. If in your code you are accessing the accelerator from multiple threads (or, in general, from different parts of your app), then you'll want to create separate accelerator_view objects for each thread. flush, wait, and queuing_mode When you create an accelerator_view via the create_view method of the accelerator, you pass in an option of immediate or deferred, which are the two members of the queuing_mode enum. At any point you can access this value from the queuing_mode property of the accelerator_view. When the queuing_mode value is immediate (which is the default), any commands sent to the device such as kernel invocations and data transfers (e.g. parallel_for_each and copy, as we'll see in future posts), will get submitted as soon as the runtime sees fit (that is the definition of immediate). When the value of queuing_mode is deferred, the commands will be batched up. To send all buffered commands to the device for execution, there is a non-blocking flush method that you can call. If you wish to block until all the commands have been sent, there is a wait method you can call. Deferring is a more advanced scenario aimed at performance gains when you are submitting many device commands and you want to avoid the tiny overhead of flushing/submitting each command separately. Querying information Just like accelerator, accelerator_view exposes the is_debug and version properties. In fact, you can always access the accelerator object from the accelerator property on the accelerator_view class to access the accelerator interface we looked at previously. Interop with D3D (aka DX) In a later post I'll show an example of an app that uses C++ AMP to compute data that is used in pixel shaders. In those scenarios, you can benefit by integrating C++ AMP into your graphics pipeline and one of the building blocks for that is being able to use the same device context from both the compute kernel and the other shaders. You can do that by going from accelerator_view to device context (and vice versa), through part of our interop API in amp.h: *get_device, create_accelerator_view. More on those in a later post. Comments about this post by Daniel Moth welcome at the original blog.

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• MvcExtensions - ActionFilter

  - by kazimanzurrashid

  One of the thing that people often complains is dependency injection in Action Filters. Since the standard way of applying action filters is to either decorate the Controller or the Action methods, there is no way you can inject dependencies in the action filter constructors. There are quite a few posts on this subject, which shows the property injection with a custom action invoker, but all of them suffers from the same small bug (you will find the BuildUp is called more than once if the filter implements multiple interface e.g. both IActionFilter and IResultFilter). The MvcExtensions supports both property injection as well as fluent filter configuration api. There are a number of benefits of this fluent filter configuration api over the regular attribute based filter decoration. You can pass your dependencies in the constructor rather than property. Lets say, you want to create an action filter which will update the User Last Activity Date, you can create a filter like the following: public class UpdateUserLastActivityAttribute : FilterAttribute, IResultFilter { public UpdateUserLastActivityAttribute(IUserService userService) { Check.Argument.IsNotNull(userService, "userService"); UserService = userService; } public IUserService UserService { get; private set; } public void OnResultExecuting(ResultExecutingContext filterContext) { // Do nothing, just sleep. } public void OnResultExecuted(ResultExecutedContext filterContext) { Check.Argument.IsNotNull(filterContext, "filterContext"); string userName = filterContext.HttpContext.User.Identity.IsAuthenticated ? filterContext.HttpContext.User.Identity.Name : null; if (!string.IsNullOrEmpty(userName)) { UserService.UpdateLastActivity(userName); } } } As you can see, it is nothing different than a regular filter except that we are passing the dependency in the constructor. Next, we have to configure this filter for which Controller/Action methods will execute: public class ConfigureFilters : ConfigureFiltersBase { protected override void Configure(IFilterRegistry registry) { registry.Register<HomeController, UpdateUserLastActivityAttribute>(); } } You can register more than one filter for the same Controller/Action Methods: registry.Register<HomeController, UpdateUserLastActivityAttribute, CompressAttribute>(); You can register the filters for a specific Action method instead of the whole controller: registry.Register<HomeController, UpdateUserLastActivityAttribute, CompressAttribute>(c => c.Index()); You can even set various properties of the filter: registry.Register<ControlPanelController, CustomAuthorizeAttribute>( attribute => { attribute.AllowedRole = Role.Administrator; }); The Fluent Filter registration also reduces the number of base controllers in your application. It is very common that we create a base controller and decorate it with action filters and then we create concrete controller(s) so that the base controllers action filters are also executed in the concrete controller. You can do the  same with a single line statement with the fluent filter registration: Registering the Filters for All Controllers: registry.Register<ElmahHandleErrorAttribute>(new TypeCatalogBuilder().Add(GetType().Assembly).Include(type => typeof(Controller).IsAssignableFrom(type))); Registering Filters for selected Controllers: registry.Register<ElmahHandleErrorAttribute>(new TypeCatalogBuilder().Add(GetType().Assembly).Include(type => typeof(Controller).IsAssignableFrom(type) && (type.Name.StartsWith("Home") || type.Name.StartsWith("Post")))); You can also use the built-in filters in the fluent registration, for example: registry.Register<HomeController, OutputCacheAttribute>(attribute => { attribute.Duration = 60; }); With the fluent filter configuration you can even apply filters to controllers that source code is not available to you (may be the controller is a part of a third part component). That’s it for today, in the next post we will discuss about the Model binding support in MvcExtensions. So stay tuned.

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• Abstracting entity caching in XNA

  - by Grofit

  I am in a situation where I am writing a framework in XNA and there will be quite a lot of static (ish) content which wont render that often. Now I am trying to take the same sort of approach I would use when doing non game development, where I don't even think about caching until I have finished my application and realise there is a performance problem and then implement a layer of caching over whatever needs it, but wrap it up so nothing is aware its happening. However in XNA the way we would usually cache would be drawing our objects to a texture and invalidating after a change occurs. So if you assume an interface like so: public interface IGameComponent { void Update(TimeSpan elapsedTime); void Render(GraphicsDevice graphicsDevice); } public class ContainerComponent : IGameComponent { public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it } public void Render(GraphicsDevice graphicsDevice) { foreach(var component in ChildComponents) { // draw every component } } } Then I was under the assumption that we just draw everything directly to the screen, then when performance becomes an issue we just add a new implementation of the above like so: public class CacheableContainerComponent : IGameComponent { private Texture2D cachedOutput; private bool hasChanged; public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it // set hasChanged to true if required } public void Render(GraphicsDevice graphicsDevice) { if(hasChanged) { CacheComponents(graphicsDevice); } // Draw cached output } private void CacheComponents(GraphicsDevice graphicsDevice) { // Clean up existing cache if needed var cachedOutput = new RenderTarget2D(...); graphicsDevice.SetRenderTarget(renderTarget); foreach(var component in ChildComponents) { // draw every component } graphicsDevice.SetRenderTarget(null); } } Now in this example you could inherit, but your Update may become a bit tricky then without changing your base class to alert you if you had changed, but it is up to each scenario to choose if its inheritance/implementation or composition. Also the above implementation will re-cache within the rendering cycle, which may cause performance stutters but its just an example of the scenario... Ignoring those facts as you can see that in this example you could use a cache-able component or a non cache-able one, the rest of the framework needs not know. The problem here is that if lets say this component is drawn mid way through the game rendering, other items will already be within the default drawing buffer, so me doing this would discard them, unless I set it to be persisted, which I hear is a big no no on the Xbox. So is there a way to have my cake and eat it here? One simple solution to this is make an ICacheable interface which exposes a cache method, but then to make any use of this interface you would need the rest of the framework to be cache aware, and check if it can cache, and to then do so. Which then means you are polluting and changing your main implementations to account for and deal with this cache... I am also employing Dependency Injection for alot of high level components so these new cache-able objects would be spat out from that, meaning no where in the actual game would they know they are caching... if that makes sense. Just incase anyone asked how I expected to keep it cache aware when I would need to new up a cachable entity.

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• How do I use setFilmSize in panda3d to achieve the correct view?

  - by lhk

  I'm working with Panda3d and recently switched my game to isometric rendering. I moved the virtual camera accordingly and set an orthographic lens. Then I implemented the classes "Map" and "Canvas". A canvas is a dynamically generated mesh: a flat quad. I'm using it to render the ingame graphics. Since the game itself is still set in a 3d coordinate system I'm planning to rely on these canvases to draw sprites. I could have named this class "Tile" but as I'd like to use it for non-tile sketches (enemies, environment) as well I thought canvas would describe it's function better. Map does exactly what it's name suggests. Its constructor receives the number of rows and columns and then creates a standard isometric map. It uses the canvas class for tiles. I'm planning to write a map importer that reads a file to create maps on the fly. Here's the canvas implementation: class Canvas: def __init__(self, texture, vertical=False, width=1,height=1): # create the mesh format=GeomVertexFormat.getV3t2() format = GeomVertexFormat.registerFormat(format) vdata=GeomVertexData("node-vertices", format, Geom.UHStatic) vertex = GeomVertexWriter(vdata, 'vertex') texcoord = GeomVertexWriter(vdata, 'texcoord') # add the vertices for a flat quad vertex.addData3f(1, 0, 0) texcoord.addData2f(1, 0) vertex.addData3f(1, 1, 0) texcoord.addData2f(1, 1) vertex.addData3f(0, 1, 0) texcoord.addData2f(0, 1) vertex.addData3f(0, 0, 0) texcoord.addData2f(0, 0) prim = GeomTriangles(Geom.UHStatic) prim.addVertices(0, 1, 2) prim.addVertices(2, 3, 0) self.geom = Geom(vdata) self.geom.addPrimitive(prim) self.node = GeomNode('node') self.node.addGeom(self.geom) # this is the handle for the canvas self.nodePath=NodePath(self.node) self.nodePath.setSx(width) self.nodePath.setSy(height) if vertical: self.nodePath.setP(90) # the most important part: "Drawing" the image self.texture=loader.loadTexture(""+texture+".png") self.nodePath.setTexture(self.texture) Now the code for the Map class class Map: def __init__(self,rows,columns,size): self.grid=[] for i in range(rows): self.grid.append([]) for j in range(columns): # create a canvas for the tile. For testing the texture is preset tile=Canvas(texture="../assets/textures/flat_concrete",width=size,height=size) x=(i-1)*size y=(j-1)*size # set the tile up for rendering tile.nodePath.reparentTo(render) tile.nodePath.setX(x) tile.nodePath.setY(y) # and store it for later access self.grid[i].append(tile) And finally the usage def loadMap(self): self.map=Map(10, 10, 1) this function is called within the constructor of the World class. The instantiation of world is the entry point to the execution. The code is pretty straightforward and runs good. Sadly the output is not as expected: Please note: The problem is not the white rectangle, it's my player object. The problem is that although the map should have equal width and height it's stretched weirdly. With orthographic rendering I expected the map to be a perfect square. What did I do wrong ? UPDATE: I've changed the viewport. This is how I set up the orthographic camera: lens = OrthographicLens() lens.setFilmSize(40, 20) base.cam.node().setLens(lens) You can change the "aspect" by modifying the parameters of setFilmSize. I don't know exactly how they are related to window size and screen resolution but after testing a little the values above seem to work for me. Now everything is rendered correctly as long as I don't resize the window. Every change of the window's size as well as switching to fullscreen destroys the correct rendering. I know that implementing a listener for resize events is not in the scope of this question. However I wonder why I need to make the Film's height two times bigger than its width. My window is quadratic ! Can you tell me how to find out correct setting for the FilmSize ? UPDATE 2: I can imagine that it's hard to envision the behaviour of the game. At first glance the obvious solution is to pass the window's width and height in pixels to setFilmSize. There are two problems with that approach. The parameters for setFilmSize are ingame units. You'll get a way to big view if you pass the pixel size For some strange reason the image is distorted if you pass equal values for width and height. Here's the output for setFilmSize(800,800) You'll have to stress your eyes but you'll see what I mean

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• How to layout class definition when inheriting from multiple interfaces

  - by gabr

  Given two interface definitions ... IOmniWorkItem = interface ['{3CE2762F-B7A3-4490-BF22-2109C042EAD1}'] function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); // procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; end; IOmniWorkItemEx = interface ['{3B48D012-CF1C-4B47-A4A0-3072A9067A3E}'] function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); // property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; ... what are your ideas of laying out class declaration that inherits from both of them? My current idea (but I don't know if I'm happy with it): TOmniWorkItem = class(TInterfacedObject, IOmniWorkItem, IOmniWorkItemEx) strict private FData : TOmniValue; FOnWorkItemDone : TOmniWorkItemDoneDelegate; FOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; FResult : TOmniValue; FUniqueID : int64; strict protected procedure FreeException; protected //IOmniWorkItem function GetData: TOmniValue; function GetResult: TOmniValue; function GetUniqueID: int64; procedure SetResult(const value: TOmniValue); protected //IOmniWorkItemEx function GetOnWorkItemDone: TOmniWorkItemDoneDelegate; function GetOnWorkItemDone_Asy: TOmniWorkItemDoneDelegate; procedure SetOnWorkItemDone(const Value: TOmniWorkItemDoneDelegate); procedure SetOnWorkItemDone_Asy(const Value: TOmniWorkItemDoneDelegate); public constructor Create(const data: TOmniValue; uniqueID: int64); destructor Destroy; override; public //IOmniWorkItem procedure Cancel; function DetachException: Exception; function FatalException: Exception; function IsCanceled: boolean; function IsExceptional: boolean; property Data: TOmniValue read GetData; property Result: TOmniValue read GetResult write SetResult; property UniqueID: int64 read GetUniqueID; public //IOmniWorkItemEx property OnWorkItemDone: TOmniWorkItemDoneDelegate read GetOnWorkItemDone write SetOnWorkItemDone; property OnWorkItemDone_Asy: TOmniWorkItemDoneDelegate read GetOnWorkItemDone_Asy write SetOnWorkItemDone_Asy; end; As noted in answers, composition is a good approach for this example but I'm not sure it applies in all cases. Sometimes I'm using multiple inheritance just to split read and write access to some property into public (typically read-only) and private (typically write-only) part. Does composition still apply here? I'm not really sure as I would have to move the property in question out from the main class and I'm not sure that's the correct way to do it. Example: // public part of the interface interface IOmniWorkItemConfig = interface function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; end; // private part of the interface IOmniWorkItemConfigEx = interface ['{42CEC5CB-404F-4868-AE81-6A13AD7E3C6B}'] function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end; // implementing class TOmniWorkItemConfig = class(TInterfacedObject, IOmniWorkItemConfig, IOmniWorkItemConfigEx) strict private FOnExecute : TOmniBackgroundWorkerDelegate; FOnRequestDone : TOmniWorkItemDoneDelegate; FOnRequestDone_Asy: TOmniWorkItemDoneDelegate; public constructor Create(defaults: IOmniWorkItemConfig = nil); public //IOmniWorkItemConfig function OnExecute(const aTask: TOmniBackgroundWorkerDelegate): IOmniWorkItemConfig; function OnRequestDone(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; function OnRequestDone_Asy(const aTask: TOmniWorkItemDoneDelegate): IOmniWorkItemConfig; public //IOmniWorkItemConfigEx function GetOnExecute: TOmniBackgroundWorkerDelegate; function GetOnRequestDone: TOmniWorkItemDoneDelegate; function GetOnRequestDone_Asy: TOmniWorkItemDoneDelegate; end;

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• Entity System with C++ templates

  - by tommaisey

  I've been getting interested in the Entity/Component style of game programming, and I've come up with a design in C++ which I'd like a critique of. I decided to go with a fairly pure Entity system, where entities are simply an ID number. Components are stored in a series of vectors - one for each Component type. However, I didn't want to have to add boilerplate code for every new Component type I added to the game. Nor did I want to use macros to do this, which frankly scare me. So I've come up with a system based on templates and type hinting. But there are some potential issues I'd like to check before I spend ages writing this (I'm a slow coder!) All Components derive from a Component base class. This base class has a protected constructor, that takes a string parameter. When you write a new derived Component class, you must initialise the base with the name of your new class in a string. When you first instantiate a new DerivedComponent, it adds the string to a static hashmap inside Component mapped to a unique integer id. When you subsequently instantiate more Components of the same type, no action is taken. The result (I think) should be a static hashmap with the name of each class derived from Component that you instantiate at least once, mapped to a unique id, which can by obtained with the static method Component::getTypeId ("DerivedComponent"). Phew. The next important part is TypedComponentList<typename PropertyType>. This is basically just a wrapper to an std::vector<typename PropertyType> with some useful methods. It also contains a hashmap of entity ID numbers to slots in the array so we can find Components by their entity owner. Crucially TypedComponentList<> is derived from the non-template class ComponentList. This allows me to maintain a list of pointers to ComponentList in my main ComponentManager, which actually point to TypedComponentLists with different template parameters (sneaky). The Component manager has template functions such as: template <typename ComponentType> void addProperty (ComponentType& component, int componentTypeId, int entityId) and: template <typename ComponentType> TypedComponentList<ComponentType>* getComponentList (int componentTypeId) which deal with casting from ComponentList to the correct TypedComponentList for you. So to get a list of a particular type of Component you call: TypedComponentList<MyComponent>* list = componentManager.getComponentList<MyComponent> (Component::getTypeId("MyComponent")); Which I'll admit looks pretty ugly. Bad points of the design: If a user of the code writes a new Component class but supplies the wrong string to the base constructor, the whole system will fail. Each time a new Component is instantiated, we must check a hashed string to see if that component type has bee instantiated before. Will probably generate a lot of assembly because of the extensive use of templates. I don't know how well the compiler will be able to minimise this. You could consider the whole system a bit complex - perhaps premature optimisation? But I want to use this code again and again, so I want it to be performant. Good points of the design: Components are stored in typed vectors but they can also be found by using their entity owner id as a hash. This means we can iterate them fast, and minimise cache misses, but also skip straight to the component we need if necessary. We can freely add Components of different types to the system without having to add and manage new Component vectors by hand. What do you think? Do the good points outweigh the bad?

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• WCF ChannelFactory caching

  - by Myles J

  I've just read this great article on WCF ChannelFactory caching by Wenlong Dong. My question is simply how can you actually prove that the ChannelFactory is in fact being cached between calls? I've followed the rules regarding the ClientBase’s constructors. We are using the following overloaded constructor on our object that inherits from ClientBase: ClientBase(string endpointConfigurationName, EndpointAddress remoteAddress); In the article mentioned above it is stated that: For these constructors, all arguments (including default ones) are in the following list: · InstanceContext callbackInstance · string endpointConfigurationName · EndpointAddress remoteAddress As long as these three arguments are the same when ClientBase is constructed, we can safely assume that the same ChannelFactory can be used. Fortunately, String and EndpointAddress types are immutable, i.e., we can make simple comparison to determine whether two arguments are the same. For InstanceContext, we can use Object reference comparison. The type EndpointTrait is thus used as the key of the MRU cache. To test the ChannelFactory cache theory we are checking the Hashcode in the ClientBase constructor e.g. var testHash = RuntimeHelpers.GetHashCode(base.ChannelFactory); The hash value is different between calls which makes us think that the ChannelFactory isn't actually cached. Any thoughts? Regards Myles

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• Injecting Mockito mocks into a Spring bean

  - by teabot

  I would like to inject a Mockito mock object into a Spring (3+) bean for the purposes of unit testing with JUnit. My bean dependencies are currently injected by using the @Autowired annotation on private member fields. I have considered using ReflectionTestUtils.setField but the bean instance that I wish to inject is actually a proxy and hence does not declare the private member fields of the target class. I do not wish to create a public setter to the dependency as I will then be modifying my interface purely for the purposes of testing. I have followed some advice given by the Spring community but the mock does not get created and the auto-wiring fails: <bean id="dao" class="org.mockito.Mockito" factory-method="mock"> <constructor-arg value="com.package.Dao" /> </bean> The error I currently encounter is as follows: ... Caused by: org...NoSuchBeanDefinitionException: No matching bean of type [com.package.Dao] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: { @org...Autowired(required=true), @org...Qualifier(value=dao) } at org...DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(D...y.java:901) at org...DefaultListableBeanFactory.doResolveDependency(D...y.java:770) If I set the constructor-arg value to something invalid no error occurs when starting the application context.

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