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• Logic in Entity Components Sytems

  - by aaron

  I'm making a game that uses an Entity/Component architecture basically a port of Artemis's framework to c++,the problem arises when I try to make a PlayerControllerComponent, my original idea was this. class PlayerControllerComponent: Component { public: virtual void update() = 0; }; class FpsPlayerControllerComponent: PlayerControllerComponent { public: void update() { //handle input } }; and have a system that updates PlayerControllerComponents, but I found out that the artemis framework does not look at sub-classes the way I thought it would. So all in all my question here is should I make the framework aware of subclasses or should I add a new Component like object that is used for logic.

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• How do I make camera move at same speed when rotating and moving forward

  - by dez

  I made a camera in DX9. To move forward I press the Up arrow. To rotate on the Y axis I use the mouse. When I perform these movements on their own the camera moves at the speed I want. However, if I hold down Up and move the mouse at the same time then the camera moves a lot faster than it should. I want it to move at the same speed as it does when only the Up arrow is pressed. I think I need to normalize something somewhere but not sure what and not sure where. Have tried various combinations without success so if anyone can point me in the right direction that would be great. Thanks. I've post code below. #define KEY_DOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0) LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ) { if( KEY_DOWN(VK_UP)) MovePlayer(D3DXVECTOR3(0, 0, -1.0f)); if( KEY_DOWN(VK_DOWN)) MovePlayer(D3DXVECTOR3(0, 0, 1.0f)); switch( msg ) { case WM_MOUSEMOVE: ProcessMouseInput(); } } void MovePlayer( D3DXVECTOR3 in_vec ) { D3DXMATRIX CameraRot; D3DXMatrixRotationY(&CameraRot,D3DXToRadian(AngleY)); D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&in_vec,&CameraRot); CameraPos += (m_timeElapsed * CameraRotTarget); } void ProcessMouseInput() { GetCursorPos( &CurrentMouseState ); if ((CurrentMouseState.x != GameMouseState.x) || (CurrentMouseState.y != GameMouseState.y)) { int dx = CurrentMouseState.x - GameMouseState.x; int dy = CurrentMouseState.y - GameMouseState.y; AngleY+=m_timeElapsed*dx*7.0f; } GameMouseState = CurrentMouseState; // Set back to window center in Render function } VOID UpdateCamera() { D3DXVECTOR3 CameraOrigTarget(0, 0, -1); D3DXVECTOR3 CameraOrigUp(0, 1, 0); D3DXMATRIX CameraRot; D3DXMATRIX CameraRotX; D3DXMatrixRotationX(&CameraRotX,D3DXToRadian(AngleX)); D3DXMATRIX CameraRotY; D3DXMatrixRotationY(&CameraRotY,D3DXToRadian(AngleY)); CameraRot = CameraRotX * CameraRotY; D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&CameraOrigTarget,&CameraRot); D3DXVECTOR3 CameraTarget; CameraTarget = CameraPos + CameraRotTarget; D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f ); D3DXMatrixLookAtLH( &matView, &CameraPos, &CameraTarget, &vUpVec ); g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView ); D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI / 4, 1.0f, 1.0f, 100.0f ); g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj ); }

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• Why is my collision detection not accurate?

  - by optimisez

  After trying and trying, I still cannot understand why the leg of character exceeds the wall but no clipping issue when I hit the wall from below. How should I fix it to make him stand still on the wall? From collideWithBox() function below, it shows that playerDest.Y = boxDest.Y - boxDest.height; will get the position the character should standstill on the wall. Theoretically, the clipping effect won't be happen as the character hit the box from below works with the equation playerDest.Y = boxDest.Y + boxDest.height;. void collideWithBox() { if ( spriteCollide(playerDest, boxDest) && keyArr[VK_UP]) //playerDest.Y += 50; playerDest.Y = boxDest.Y + boxDest.height; else if ( spriteCollide(playerDest, boxDest) && !keyArr[VK_UP]) playerDest.Y = boxDest.Y - boxDest.height; } void initPlayer() { // Create texture. hr = D3DXCreateTextureFromFileEx(d3dDevice, "player.png", 169, 44, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &player); playerRect.left = playerRect.top = 0; playerRect.right = 29; playerRect.bottom = 36; playerDest.X = 0; playerDest.Y = 564; playerDest.length = playerRect.right - playerRect.left; playerDest.height = playerRect.bottom - playerRect.top; } void initBox() { hr = D3DXCreateTextureFromFileEx(d3dDevice, "brock.png", 330, 132, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 255), NULL, NULL, &box); boxRect.left = 33; boxRect.top = 0; boxRect.right = 63; boxRect.bottom = 30; boxDest.X = boxDest.Y = 300; boxDest.length = boxRect.right - boxRect.left; boxDest.height = boxRect.bottom - boxRect.top; } bool spriteCollide(Entity player, Entity target) { float left1, left2; float right1, right2; float top1, top2; float bottom1, bottom2; left1 = player.X; left2 = target.X; right1 = player.X + player.length; right2 = target.X + target.length; top1 = player.Y; top2 = target.Y; bottom1 = player.Y + player.height; bottom2 = target.Y + target.height; if (bottom1 < top2) return false; if (top1 > bottom2) return false; if (right1 < left2) return false; if (left1 > right2) return false; return true; }

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• Placing advice on any parameter of a given type in AspectJ

  - by user12558

  Hi, Im doing a POC using Aspectj. class BaseInfo{..} class UserInfo extends BaseInfo{..} class UserService { public void getUser(UserInfo userInfo){..} public void deleteUser(String userId){..} } I've defined an advice, that gets invoked when I pass an UserInfo instance.But when i try to pass the BaseInfo, the advice is not getting invoked. Below block executes the afterMethod as expected for getUser. &ltaop:pointcut id="aopafterMethod" expression="execution(* UserService.*(..,UserInfo,..))" / &gtaop:after pointcut-ref="aopafterMethod" method="afterMethod" / But when i try to give BaseInfo instead of UserInfo, the aspect is not getting triggered. Am i missing something? Kindly help me on this issue.

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• What Do You Think About This Smelly Test?

  - by panamack

  I caught a whiff of a smell eminating from one of my tests, in a scenario akin to the following: [TestFixture] public void CarPresenterTests{ [Test] public void Throws_If_Cars_Wheels_Collection_Is_Null(){ IEnumerable<Wheels> wheels = null; var car = new Car(wheels); Assert.That( ()=>new CarPresenter(car), Throws.InstanceOf<ArgumentException>() .With.Message.EqualTo("Can't create if cars wheels is null)); } } public class CarPresenter{ public CarPresenter(Car car) { if(car.Wheels == null) throw new ArgumentException("Can't create if cars wheels is null); _car = car; _car.Wheels.Rolling += WheelsRollingHandler; } } I was struggling to describe what the problem is except that it seems wrong that a CarPresenter should attempt to dictate to a Car whether or not it's Wheels are initialised correctly. I wondered what pointers people here might give me?

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• Invoking JavaScript from Java

  - by Geertjan

  Here's an Action class defined in Java. The Action class executes a script via the JavaFX WebEngine: @NbBundle.Messages("CTL_AddBananasAction=Add Banana") private class AddBananasAction extends AbstractAction { public AddBananasAction() { super(Bundle.CTL_AddBananasAction()); } @Override public void actionPerformed(ActionEvent e) { Platform.runLater(new Runnable() { @Override public void run() { webengine.executeScript("addBanana(' " + newBanana + " ') "); } }); } }How does the 'executescript' call know where to find the JavaScript file? Well, earlier in the code, the WebEngine loaded an HTML file, where the JavaScript file was registered: WebView view = new WebView(); view.setMinSize(widthDouble, heightDouble); view.setPrefSize(widthDouble, heightDouble); webengine = view.getEngine(); URL url = getClass().getResource("home.html"); webengine.load(url.toExternalForm()); Finally, here's a skeleton 'addBanana' method, which is invoked via the Action class shown above: function addBanana(user){ statustext.text(user); } By the way, if you have your JavaScript and CSS embedded within your HTML file, the code navigator combines all three into the same window, which is kind of cool:

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• C/C++ canonicaliser?

  - by A T

  Are there any C/C++ automated canonicallisers? - Something like astyle but which makes your code more concise, rather than formats it? For example, to go from: float foo() { float a; float b; a = 9455.34; b = 3543.8; return a*b; } int main(void) { float b; b = foo(); return 0; } To: float foo(); // Automated prototype creation int main(void) { float b = foo(); return 0; } float foo() { return 9455.34*3543.8; } (this is my coding style FYI: to reduce the lines-of-code without sacrificing readability)

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• Using extension methods to decrease the surface area of a C# interface

  - by brian_ritchie

  An interface defines a contract to be implemented by one or more classes.  One of the keys to a well-designed interface is defining a very specific range of functionality. The profile of the interface should be limited to a single purpose & should have the minimum methods required to implement this functionality.  Keeping the interface tight will keep those implementing the interface from getting lazy & not implementing it properly.  I've seen too many overly broad interfaces that aren't fully implemented by developers.  Instead, they just throw a NotImplementedException for the method they didn't implement. One way to help with this issue, is by using extension methods to move overloaded method definitions outside of the interface. Consider the following example: .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: Consolas, "Courier New", Courier, Monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: public interface IFileTransfer 2: { 3: void SendFile(Stream stream, Uri destination); 4: } 5:   6: public static class IFileTransferExtension 7: { 8: public static void SendFile(this IFileTransfer transfer, 9: string Filename, Uri destination) 10: { 11: using (var fs = File.OpenRead(Filename)) 12: { 13: transfer.SendFile(fs, destination); 14: } 15: } 16: } 17:   18: public static class TestIFileTransfer 19: { 20: static void Main() 21: { 22: IFileTransfer transfer = new FTPFileTransfer("user", "pass"); 23: transfer.SendFile(filename, new Uri("ftp://ftp.test.com")); 24: } 25: } In this example, you may have a number of overloads that uses different mechanisms for specifying the source file. The great part is, you don't need to implement these methods on each of your derived classes.  This gives you a better interface and better code reuse.

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• Using T[1] instead of T for functions overloaded for T(&)[N]

  - by Abyx

  The asio::buffer function has (void*, size_t) and (PodType(&)[N]) overloads. I didn't want to write ugly C-style (&x, sizeof(x)) code, so I wrote this: SomePacket packet[1]; // SomePacket is POD read(socket, asio::buffer(packet)); foo = packet->foo; But that packet-> looks kinda weird - the packet is an array after all. (And packet[0]. doesn't look better.) Now, I think if it was a good idea to write such code. Maybe I should stick to unsafe C-style code with void* and sizeof? Upd: here is another example, for writing a packet: SomePacket packet[1]; // SomePacket is POD packet->id = SomePacket::ID; packet->foo = foo; write(socket, asio::buffer(packet));

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• What are the best practices to use NHiberante sessions in asp.net (mvc/web api) ?

  - by mrt181

  I have the following setup in my project: public class WebApiApplication : System.Web.HttpApplication { public static ISessionFactory SessionFactory { get; private set; } public WebApiApplication() { this.BeginRequest += delegate { var session = SessionFactory.OpenSession(); CurrentSessionContext.Bind(session); }; this.EndRequest += delegate { var session = SessionFactory.GetCurrentSession(); if (session == null) { return; } session = CurrentSessionContext.Unbind(SessionFactory); session.Dispose(); }; } protected void Application_Start() { AreaRegistration.RegisterAllAreas(); FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters); RouteConfig.RegisterRoutes(RouteTable.Routes); BundleConfig.RegisterBundles(BundleTable.Bundles); var assembly = Assembly.GetCallingAssembly(); SessionFactory = new NHibernateHelper(assembly, Server.MapPath("/")).SessionFactory; } } public class PositionsController : ApiController { private readonly ISession session; public PositionsController() { this.session = WebApiApplication.SessionFactory.GetCurrentSession(); } public IEnumerable<Position> Get() { var result = this.session.Query<Position>().Cacheable().ToList(); if (!result.Any()) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.NotFound)); } return result; } public HttpResponseMessage Post(PositionDataTransfer dto) { //TODO: Map dto to model IEnumerable<Position> positions = null; using (var transaction = this.session.BeginTransaction()) { this.session.SaveOrUpdate(positions); try { transaction.Commit(); } catch (StaleObjectStateException) { if (transaction != null && transaction.IsActive) { transaction.Rollback(); } } } var response = this.Request.CreateResponse(HttpStatusCode.Created, dto); response.Headers.Location = new Uri(this.Request.RequestUri.AbsoluteUri + "/" + dto.Name); return response; } public void Put(int id, string value) { //TODO: Implement PUT throw new NotImplementedException(); } public void Delete(int id) { //TODO: Implement DELETE throw new NotImplementedException(); } } I am not sure if this is the recommended way to insert the session into the controller. I was thinking about using DI but i am not sure how to inject the session that is opened and binded in the BeginRequest delegate into the Controllers constructor to get this public PositionsController(ISession session) { this.session = session; } Question: What is the recommended way to use NHiberante sessions in asp.net mvc/web api ?

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• Have I mistakenly assumed that my routines are loosely coupled?

  - by Tarun

  My Selenium test structures goes as - Data Object class - public class RegistrationData { String firstName = "test first name"; String lastName = "test last name"; // Getter Setter Here } Page Object class which carries out operations on a Web Page - public class RegistrationPage { private RegistrationData regData; public void setRegistrationData(RegistrationData regData) { this.regData = regData(); public NewAccountPage fillRegForm() { enterFirstName("FirstNameTextBoxLocator", regData.getFirstName); enterLastName("LastNameTextBoxLocator", regData.getLastName); // Some more fields are filled here return NewAccountPage(); } } And test class uses them as - public class TestRegistration extends SelTestCase { @Test public void testRegNewUser() { RegistrationData regData = new RegistrationData(); RegistrationPage regPage = New RegistrationPage(); regPage.setRegistrationData(regData) regPage.fillRegForm(); // Some assertion here } } Now since fillRegForm method does not take any argument, Can I assume that it is an example of loose coupling despite I need to set RegistrationData in RegistrationPage before being able to use fillRegForm method.

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• Is this a violation of the Liskov Substitution Principle?

  - by Paul T Davies

  Say we have a list of Task entities, and a ProjectTask sub type. Tasks can be closed at any time, except ProjectTasks which cannot be closed once they have a status of Started. The UI should ensure the option to close a started ProjectTask is never available, but some safeguards are present in the domain: public class Task { public Status Status { get; set; } public virtual void Close() { Status = Status.Closed; } } public ProjectTask : Task { public override void Close() { if (Status == Status.Started) throw new Exception("Cannot close a started Project Task"); base.Close(); } } Now when calling Close() on a Task, there is a chance the call will fail if it is a ProjectTask with the started status, when it wouldn't if it was a base Task. But this is the business requirements. It should fail. Can this be regarded as a violation?

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• How do I make a dialog box? [on hold]

  - by bill

  By dialog box I mean when player talks to someone, a box shows up with text on it. I haven't found much about this topic online, so I created a basic dialog box: //in dialog box i have only two methods public void createBox(int x, int y, int width, int height, String txt) { this.x = x; this.y = y; this.width = width; this.height = height; this.txt = txt; } //draw dialog box public void draw(Graphics2D g) { if (txt != null) { g.setColor(Color.red); g.drawRect(x,y,width,height); g.setColor(Color.black); g.fillRect(x, y, width, height); g.setColor(Color.white); g.drawString(txt, x + 10, y + 10); } } I wanted to now can I make this better?

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• Accepting a numerical range in a function call

  - by dekpos

  I have encountered two ways of doing it: void foo(int from, int to); /* 'from' inclusive, 'to' exclusive */ void foo(int startIndex, int rangelength); Has one style historically been preferred over the other? If so, was it just a matter of convention or was it due to some deeper underlying reason? I'm currently programming in Java and noticed that the Arrays class uses the former style. The exclusivity of the to argument felt somewhat unintuitive to me, which led me to ask this question.

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• How can I combine my FTP queries? [migrated]

  - by ryansworld10

  My program has several times where it queries an FTP server to read and upload information. How can I combine all these into one FTP class to handle everything? private static void UploadToFTP(string[] FTPSettings) { try { FtpWebRequest request = (FtpWebRequest)WebRequest.Create(FTPSettings[0]); request.Method = WebRequestMethods.Ftp.MakeDirectory; request.Credentials = new NetworkCredential(FTPSettings[1], FTPSettings[2]); FtpWebResponse response = (FtpWebResponse)request.GetResponse(); } catch { } try { FtpWebRequest request = (FtpWebRequest)WebRequest.Create(FTPSettings[0] + Path.GetFileName(file)); request.Method = WebRequestMethods.Ftp.UploadFile; request.Credentials = new NetworkCredential(FTPSettings[1], FTPSettings[2]); StreamReader source = new StreamReader(file); byte[] fileContents = Encoding.UTF8.GetBytes(source.ReadToEnd()); source.Close(); request.ContentLength = fileContents.Length; Stream requestStream = request.GetRequestStream(); requestStream.Write(fileContents, 0, fileContents.Length); requestStream.Close(); FtpWebResponse response = (FtpWebResponse)request.GetResponse(); response.Close(); RegenLog(); } catch (Exception e) { File.AppendAllText(file, string.Format("{0}{0}Upload Failed - ({2}) - {1}{0}", nl, System.DateTime.Now, e.Message.ToString())); } } private static void CheckBlacklist(string[] FTPSettings) { try { FtpWebRequest request = (FtpWebRequest)WebRequest.Create(FTPSettings[0] + "blacklist.txt"); request.Credentials = new NetworkCredential(FTPSettings[1], FTPSettings[2]); using (WebResponse response = request.GetResponse()) { using (Stream stream = response.GetResponseStream()) { using (TextReader reader = new StreamReader(stream)) { string blacklist = reader.ReadToEnd(); if (blacklist.Contains(Environment.UserName)) { File.AppendAllText(file, string.Format("{0}{0}Logger terminated - ({2}) - {1}{0}", nl, System.DateTime.Now, "Blacklisted")); uninstall = true; } } } } } catch (Exception e) { File.AppendAllText(file, string.Format("{0}{0}FTP Error - ({2}) - {1}{0}", nl, System.DateTime.Now, e.Message.ToString())); } } private static void CheckUpdate(string[] FTPSettings) { try { FtpWebRequest request = (FtpWebRequest)WebRequest.Create(FTPSettings[0] + "update.txt"); request.Credentials = new NetworkCredential(FTPSettings[1], FTPSettings[2]); using (WebResponse response = request.GetResponse()) { using (Stream stream = response.GetResponseStream()) { using (TextReader reader = new StreamReader(stream)) { string newVersion = reader.ReadToEnd(); if (newVersion != version) { update = true; } } } } } catch (Exception e) { File.AppendAllText(file, string.Format("{0}{0}FTP Error - ({2}) - {1}{0}", nl, System.DateTime.Now, e.Message.ToString())); } } I know my code is also a bit inconsistent and messy, however this is my first time working with FTP in C#. Please give any advice you have!

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• @OnStart & @OnStop

  - by Geertjan

  In applications based on NetBeans Platform 7.2, you'll be able to replace all your ModuleInstall classes with this code: import org.openide.modules.OnStart; import org.openide.modules.OnStop; @OnStart public final class Installer implements Runnable { @Override public void run() { System.out.println("enable something..."); } @OnStop public static final class Down implements Runnable { @Override public void run() { System.out.println("disable something..."); } } } Build the module and the annotations result in named services, thanks to @NamedServiceDefinition: Aside from no longer needing to register the ModuleInstall class in the manifest, performance of startup will be enhanced, if you use the above approach: https://netbeans.org/bugzilla/show_bug.cgi?id=200636

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• Where i set touch effect when a spawn Srite are comming on the screen?

  - by shihab_returns

  I just create a scene where create a spawn spirit that comes from above screen height in Landscape mode. Now i want to remove spirits when i touch on it. I tried but seems the code not works and crashed also after a while. here is my code: /** TimerHandler for collision detection and cleaning up */ IUpdateHandler detect = new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(float pSecondsElapsed) { Iterator<AnimatedSprite> targets = targetLL.iterator(); AnimatedSprite _target; while (targets.hasNext()) { _target = targets.next(); if (_target.getY() >= cameraHeight) { // removeSprite(_target, targets); tPool.recyclePoolItem(_target); targets.remove(); Log.d("ok", "---------Looop Inside-----"); // fail(); break; } } targetLL.addAll(TargetsToBeAdded); TargetsToBeAdded.clear(); } }; /** adds a target at a random location and let it move along the y-axis */ public void addTarget() { Random rand = new Random(); int minX = mTargetTextureRegion.getWidth(); int maxX = (int) (mCamera.getWidth() - mTargetTextureRegion.getWidth()); int rangeX = maxX - minX; Log.d("----point----", "minX:" + minX + "maxX:" + maxX + "rangeX:" + rangeX); int rX = rand.nextInt(rangeX) + minX; int rY = (int) mCamera.getHeight() + mTargetTextureRegion.getHeight(); Log.d("---Random x----", "Random x" + rX + "Random y" + rY); target = tPool.obtainPoolItem(); target.setPosition(rX, rY); target.animate(100); mMainScene.attachChild(target, 1); mMainScene.registerTouchArea(target); int minDuration = 2; int maxDuration = 32; int rangeDuration = maxDuration - minDuration; int actualDuration = rand.nextInt(rangeDuration) + minDuration; // MoveXModifier mod = new MoveXModifier(actualDuration, target.getX(), // -target.getWidth()); MoveYModifier mody = new MoveYModifier(actualDuration, -target.getHeight(), cameraHeight + 10); target.registerEntityModifier(mody.deepCopy()); TargetsToBeAdded.add(target); } @Override public boolean onAreaTouched(final TouchEvent pSceneTouchEvent, final ITouchArea pTouchArea, final float pTouchAreaLocalX, final float pTouchAreaLocalY) { if (pTouchArea == target) { Toast.makeText(getApplicationContext(), "Yoooooooo", Toast.LENGTH_LONG).show(); } return true; } ** My question is where i implements IOnAreaTouchListener in My code. ? ** Thanks in Advance.

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• How to create a Request Specific Thread Safe Static int Counter?

  - by user960567

  In one of my server application I have a class that look like, class A { static int _value = 0; void DoSomething() { // a request start here _value = 0; _value++; // a request end here } // This method can be called many time during request void SomeAsyncMethods() { _value++; } } The problem is SomeAsyncMethods is async. Can be called many times. What I need when a request start set _value = 0 and then asynchrosnously increment this. After end of request I need the total. But the problem is that another request at the same time can access the class.

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• Traversing Java Object Arrays [migrated]

  - by Sundi

  Please Help. Program does not read Array rentBooks[] in the for() loop this option is selected when choosing option 2 then option 4 in the menu The Array reads perfectly when reading the items after the setBook() Method import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; import java.io.*; import java.util.Locale; import java.text.SimpleDateFormat ; class Library { protected static String Author; protected static String Title; SimpleDateFormat PublicationDate; int itemCode; int available = 1; } class Book extends Library { protected static String PublisherName; protected static String Edition; static Book[] rentBooks = new Book[5]; //Book[] rentBooks = new Book[5]; int count = 0; public Book() { String start= "start"; showBook.main(anza); } public void setBook( String Auth, String Titl, String PublishName) { this.Author = Auth; this.Title = Titl; this.PublisherName = PublishName; } public void getBook() { //System.out.println("*************BOOKS*************************"); System.out.println( "\n\nThe Author of the first Book is "+ this.Author ); System.out.println( "The Title of the book is "+ this.Title); System.out.println( "The Publisher of the book is "+ this.PublisherName ); // System.out.println( "The Edition of the book is "+ Edition ); } } class showBook{ static Book[] rentBooks = new Book[5]; static Book[] rentBooks2 = new Book[5]; static int a,b; //for ( a=0; a < 5; a++ ) //rentBooks2[a] = new Book(); public static void main(String[] args) { File file = new File("Book2.txt"); //Book libraryBooks = new Book(); int j; //initialise Array Class Objects for( j = 0; j < 5; j++) { rentBooks[j] = new Book(); } int i = 0; try{ Scanner scanner = new Scanner(file); scanner.useDelimiter(","); String loan=""; int loan2; while( scanner.hasNextLine()) { //Should the Books be Stored in An Array? // At the moment you have separate objects stored in unknown location String Author = scanner.next(); String Title = scanner.next(); String PublisherName = scanner.next(); if ( i < 4) { System.out.println(i); rentBooks[i].setBook(Author, Title, PublisherName); rentBooks[i].getBook(); // MEMBERS SHOWN i++; } public class readBook4{ public static void main(String[] args) { int number =0; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 1 to list all items in the library "); System.out.println( "Select option 2 to list the items by category"); System.out.println( "Select option 3 to choose item available in the library "); System.out.println( "Select option 7 to exit " ); InputStreamReader isr = new InputStreamReader( System.in); BufferedReader buffer = new BufferedReader( isr); String input = ""; try { input = buffer.readLine(); number = Integer.parseInt(input); //int number = Integer.parseInt( Edition); if ( number == 1 ) { System.out.println( " \nThanks you are reading "+ input); //showStudent.main(args); showPeriodical.main(args); showDVD.main(args); // showBook.main(args); } if ( number == 2 ) { //jht.cls(); int number2; System.out.println( "Please select one of the choices below " ); System.out.println( "Select option 4 to list Books only "); System.out.println( "Select option 5 to list the Periodicals only"); System.out.println( "Select option 6 to list DVDs only"); InputStreamReader isr2 = new InputStreamReader(System.in); BufferedReader buffer2 = new BufferedReader(isr2); String input2 = ""; try { input2 = buffer2.readLine(); buffer.close(); } catch(IOException e) { System.out.println("An input error has occured"); } //System.out.println("Thanks, you are reading" + input2); number2 = Integer.parseInt(input2); if ( number2 == 4 ) { showBook.main(args); } if ( number2 == 5 ) { showPeriodical.main(args); } if ( number2 == 6 ) { showDVD.main(args); } // readBook4.main(args); } if( number == 3 ) { //showBook.main(args); showBook.availableBooks(); showDVD.availableDVD(); showPeriodical.availablePeriodical(); } if ( number == 7 ) { showStudent.main(args); } buffer.close(); } catch( IOException e ) { System.out.println( " An input error has occured "); } //System.out.println( " \nThanks you are reading "+ input); } } } //buffer.close(); scanner.close(); } catch( FileNotFoundException e) { System.out.println("File not Found"); } for ( i=0; i < 5; i++ ) rentBooks[i].getBook(); //ARRAY NOT SHOWN } }

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• Plagued by multithreaded bugs

  - by koncurrency

  On my new team that I manage, the majority of our code is platform, TCP socket, and http networking code. All C++. Most of it originated from other developers that have left the team. The current developers on the team are very smart, but mostly junior in terms of experience. Our biggest problem: multi-threaded concurrency bugs. Most of our class libraries are written to be asynchronous by use of some thread pool classes. Methods on the class libraries often enqueue long running taks onto the thread pool from one thread and then the callback methods of that class get invoked on a different thread. As a result, we have a lot of edge case bugs involving incorrect threading assumptions. This results in subtle bugs that go beyond just having critical sections and locks to guard against concurrency issues. What makes these problems even harder is that the attempts to fix are often incorrect. Some mistakes I've observed the team attempting (or within the legacy code itself) includes something like the following: Common mistake #1 - Fixing concurrency issue by just put a lock around the shared data, but forgetting about what happens when methods don't get called in an expected order. Here's a very simple example: void Foo::OnHttpRequestComplete(statuscode status) { m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } So now we have a bug in which Shutdown could get called while OnHttpNetworkRequestComplete is occuring on. A tester finds the bug, captures the crash dump, and assigns the bug to a developer. He in turn fixes the bug like this. void Foo::OnHttpRequestComplete(statuscode status) { AutoLock lock(m_cs); m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { AutoLock lock(m_cs); m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } The above fix looks good until you realize there's an even more subtle edge case. What happens if Shutdown gets called before OnHttpRequestComplete gets called back? The real world examples my team has are even more complex, and the edge cases are even harder to spot during the code review process. Common Mistake #2 - fixing deadlock issues by blindly exiting the lock, wait for the other thread to finish, then re-enter the lock - but without handling the case that the object just got updated by the other thread! Common Mistake #3 - Even though the objects are reference counted, the shutdown sequence "releases" it's pointer. But forgets to wait for the thread that is still running to release it's instance. As such, components are shutdown cleanly, then spurious or late callbacks are invoked on an object in an state not expecting any more calls. There are other edge cases, but the bottom line is this: Multithreaded programming is just plain hard, even for smart people. As I catch these mistakes, I spend time discussing the errors with each developer on developing a more appropriate fix. But I suspect they are often confused on how to solve each issue because of the enormous amount of legacy code that the "right" fix will involve touching. We're going to be shipping soon, and I'm sure the patches we're applying will hold for the upcoming release. Afterwards, we're going to have some time to improve the code base and refactor where needed. We won't have time to just re-write everything. And the majority of the code isn't all that bad. But I'm looking to refactor code such that threading issues can be avoided altogether. One approach I am considering is this. For each significant platform feature, have a dedicated single thread where all events and network callbacks get marshalled onto. Similar to COM apartment threading in Windows with use of a message loop. Long blocking operations could still get dispatched to a work pool thread, but the completion callback is invoked on on the component's thread. Components could possibly even share the same thread. Then all the class libraries running inside the thread can be written under the assumption of a single threaded world. Before I go down that path, I am also very interested if there are other standard techniques or design patterns for dealing with multithreaded issues. And I have to emphasize - something beyond a book that describes the basics of mutexes and semaphores. What do you think? I am also interested in any other approaches to take towards a refactoring process. Including any of the following: Literature or papers on design patterns around threads. Something beyond an introduction to mutexes and semaphores. We don't need massive parallelism either, just ways to design an object model so as to handle asynchronous events from other threads correctly. Ways to diagram the threading of various components, so that it will be easy to study and evolve solutions for. (That is, a UML equivalent for discussing threads across objects and classes) Educating your development team on the issues with multithreaded code. What would you do?

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• Is there a language that allows this syntax: add(elements)at(index);

  - by c_maker

  Does a language exist with such a syntax? If not, what are some of the limitations/disadvantages to this syntax in case I want to write a language that supported it? Some examples: sort(array, fromIndex, toIndex); vs sort(array)from(index1)to(index2); Method signature would like this: sort(SomeType[] arr)from(int begin)to(int end){ ... } Update: Because there might be some confusion, I'd like to clarify... I meant this question as a general idea like this (not specific to sorting and possibly using keywords like from and to): In JAVA(like language): void myfancymethod(int arg1, String arg2){ ... } myfancymethod(1, "foo"); In imaginary language: void my(int arg1)fancy(String arg2)method{ ... } my(1)fancy("foo")method;

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• Android app, No error message but has stopped unexpectedly [migrated]

  - by user74722

  Does anyone know what is my problem. I do not have any compile error messages however when i run the app it crashes and stops unexpectedly. Here is my codes. Thank you in advance. ListView l ; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_final_project); String arr[]={"Red","Green","Blue","Yellow","Cyan"}; l=(ListView) findViewById(R.id.listView1); ArrayAdapter<String> adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, arr); l.setAdapter(adapter); Button buttonOne = (Button) findViewById(R.id.button1); buttonOne.setOnClickListener(new OnClickListener(){ @Override public void onClick(View v){ setContentView(R.layout.layout_save); // setContentView(R.layout.activity_final_project); //startActivity(new Intent("com.example.finalproject.layout_save")); } }); }

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• Java game applet development

  - by RomZes

  I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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• aspect parameter validation [closed]

  - by user12558

  Hi, Im doing a POC using Aspectj. class BaseInfo{..} class UserInfo extends BaseInfo{..} class UserService { public void getUser(UserInfo userInfo){..} public void deleteUser(String userId){..} } I've defined an advice, that gets invoked when I pass an UserInfo instance.But when i try to pass the BaseInfo, the advice is not getting invoked. Below block executes the afterMethod as expected for getUser. &ltaop:pointcut id="aopafterMethod" expression="execution(* UserService.*(..,UserInfo,..))" / &gtaop:after pointcut-ref="aopafterMethod" method="afterMethod" / But when i try to give BaseInfo instead of UserInfo, the aspect is not getting triggered. Am i missing something? Kindly help me on this issue.

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• Camera not working

  - by user17548

  I made a camera in DX9. To move forward I press the Up arrow. To rotate on the Y axis I use the mouse. When I perform these movements on their own the camera moves at the speed I want. However, if I hold down Up and move the mouse at the same time then the camera moves a lot faster than it should. I want it to move at the same speed as it does when only the Up arrow is pressed. I think I need to normalize something somewhere but not sure what and not sure where. Have tried various combinations without success so if anyone can point me in the right direction that would be great. Thanks. My code #define KEY_DOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0) LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ) { if( KEY_DOWN(VK_UP)) MovePlayer(D3DXVECTOR3(0, 0, -1.0f)); if( KEY_DOWN(VK_DOWN)) MovePlayer(D3DXVECTOR3(0, 0, 1.0f)); switch( msg ) { case WM_MOUSEMOVE: ProcessMouseInput(); } } void MovePlayer( D3DXVECTOR3 in_vec ) { D3DXMATRIX CameraRot; D3DXMatrixRotationY(&CameraRot,D3DXToRadian(AngleY)); D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&in_vec,&CameraRot); CameraPos += (m_timeElapsed * CameraRotTarget); } void ProcessMouseInput() { GetCursorPos( &CurrentMouseState ); if ((CurrentMouseState.x != GameMouseState.x) || (CurrentMouseState.y != GameMouseState.y)) { int dx = CurrentMouseState.x - GameMouseState.x; int dy = CurrentMouseState.y - GameMouseState.y; AngleY+=m_timeElapsed*dx*7.0f; } GameMouseState = CurrentMouseState; // Set back to window center in Render function } VOID UpdateCamera() { D3DXVECTOR3 CameraOrigTarget(0, 0, -1); D3DXVECTOR3 CameraOrigUp(0, 1, 0); D3DXMATRIX CameraRot; D3DXMATRIX CameraRotX; D3DXMatrixRotationX(&CameraRotX,D3DXToRadian(AngleX)); D3DXMATRIX CameraRotY; D3DXMatrixRotationY(&CameraRotY,D3DXToRadian(AngleY)); CameraRot = CameraRotX * CameraRotY; D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&CameraOrigTarget,&CameraRot); D3DXVECTOR3 CameraTarget; CameraTarget = CameraPos + CameraRotTarget; D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f ); D3DXMatrixLookAtLH( &matView, &CameraPos, &CameraTarget, &vUpVec ); g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView ); D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI / 4, 1.0f, 1.0f, 100.0f ); g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj ); }

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