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  • lock shared data using c#

    - by menacheb
    Hi, I have a program (C#) with a list of tests to do. Also, I have two thread. one to add task into the list, and one to read and remove from it the performed tasks. I'm using the 'lock' function each time one of the threads want to access to the list. Another thing I want to do is, if the list is empty, the thread who need to read from the list will sleep. and wake up when the first thread add a task to the list. Here is the code I wrote: ... List<String> myList = new List(); Thread writeThread, readThread; writeThread = new Thread(write); writeThread.Start(); readThraed = new Thread(read); readThread.Start(); ... private void write() { while(...) { ... lock(myList) { myList.Add(...); } ... if (!readThread.IsAlive) { readThraed = new Thread(read); readThread.Start(); } ... } ... } private void read() { bool noMoreTasks = false; while (!noMoreTasks) { lock (MyList)//syncronize with the ADD func. { if (dataFromClientList.Count > 0) { String task = myList.First(); myList.Remove(task); } else { noMoreTasks = true; } } ... } readThread.Abort(); } Apparently I did it wrong, and it's not performed as expected (The readTread does't read from the list). Does anyone know what is my problem, and how to make it right? Many thanks,

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  • Problem with setVisible (true)

    - by Jessy
    The two examples shown below are same. Both are supposed to produce same result e.g. generate the coordinates of images displayed on JPanel. Example 1, works perfectly (print the coordinates of images), however example 2 returning 0 for the coordinate. I was wondering why because, I have put the setvisible (true) after adding the panel, in both examples. The only difference is that example 1 used extends JPanel and example 2 extends JFrame EXAMPLE 1: public class Grid extends JPanel{ public static void main(String[] args){ JFrame jf=new JFrame(); jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); final Grid grid = new Grid(); jf.add(grid); jf.pack(); Component[] components = grid.getComponents(); for (Component component : components) { System.out.println("Coordinate: "+ component.getBounds()); } jf.setVisible(true); } } EXAMPLE 2: public class Grid extends JFrame { public Grid () { setLayout(new GridBagLayout()); GridBagLayout m = new GridBagLayout(); Container c = getContentPane(); c.setLayout (m); GridBagConstraints con = new GridBagConstraints(); //construct the JPanel pDraw = new JPanel(); ... m.setConstraints(pDraw, con); pDraw.add (new GetCoordinate ()); // call new class to generate the coordinate c.add(pDraw); pack(); setVisible(true); } public static void main(String[] args) { new Grid(); } }

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  • populatin jComBobox with data from a db tbl(table) column

    - by mnmyles
    Hi guyz? I have a JComboBox which i have named "venue_JCB" i want to load details from a tbl column on form load at the initcomponets() i have declared the method "accessDBinit() ;" and after the initComponets() i have implemented the accessDBinit(); method as follows: ================================code============================ void accessDBinit() //Get Student List in the List Box { try { sql = "SELECT classLevel FROM class_session ORDER BY classLevel"; java.lang.Class.forName("com.mysql.jdbc.Driver"); Connection con2=DriverManager.getConnection("jdbc:mysql:///coast","root",""); Statement stmt2 = (Statement)con2.createStatement(); boolean hasResults = stmt2.execute(sql); if(hasResults) { ResultSet rs2 = stmt2.getResultSet(); if(rs2!=null) { displayResultsinit(rs2); } db.stmt.close(); } } catch(Exception e) { System.out.println(e+"Error in connection"); } } void displayResultsinit(ResultSet r) throws SQLException { ResultSetMetaData rmeta = r.getMetaData(); int numColumns=rmeta.getColumnCount(); while(r.next()) { for(int i=1;i<=numColumns;++i) { if(i<=numColumns) { venue_JCB.addItem(r.getString(i)); } } } } ====================================end of code=================================== the method works (Populate the combobox) but at the output bar i get the following on form load and also whenever i select a component from the combobox ======= error===== java.lang.NullPointerExceptionError in connection could some one please tell me where i am going wrong with the method? Thanks in advance regards Malachi

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  • [Cocoa] Core Animation with an NSView and subviews

    - by ndg
    I've subclassed NSView to create a 'container' view (which I've called TRTransitionView) which is being used to house two subviews. At the click of a button, I want to transition one subview out of the parent view and transition the other in, using the Core Animation transition type: kCATransitionPush. For the most part, I have this working as you'd expect (here's a basic test project I threw together). The issue I'm seeing relates to resizing my window and then toggling between my two views. After resizing a window, my subviews will appear at seemingly random locations within my TRTransitionView. Additionally, it appears as if the TRTransitionView hasn't stretched correctly and is clipping the contents of its subviews. Ideally, I would like subviews anchored to the top-left of their parent view at all times, and to also grow to expand the size of the parent view. The second issue relates to an NSTableView I've placed in my first subview. When my window is resized, and my TRTransitionView resizes to match its new dimensions, my TableView seems to resize its content quite awkwardly (the entire table seems to jolt around) and the newly expanded space that the table now occupies seems to 'flash' (as if in the process of being animated). Extremely difficult to describe, but is there any way to stop this? Here's my TRTransitionView class: -(void) awakeFromNib { [self setWantsLayer:YES]; [self addSubview:[self currentView]]; transition = [CATransition animation]; [transition setType:kCATransitionPush]; [transition setSubtype:kCATransitionFromLeft]; [self setAnimations: [NSDictionary dictionaryWithObject:transition forKey:@"subviews"]]; } - (void)setCurrentView:(NSView*)newView { if (!currentView) { currentView = newView; return; } [[self animator] replaceSubview:currentView with:newView]; currentView = newView; } -(IBAction) switchToViewOne:(id)sender { [transition setSubtype:kCATransitionFromLeft]; [self setCurrentView:viewOne]; } -(IBAction) switchToViewTwo:(id)sender { [transition setSubtype:kCATransitionFromRight]; [self setCurrentView:viewTwo]; }

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  • jQuery remove selected option from this

    - by odavy
    Hi all, first post here, I come in peace :) I've searched but can't quite find what I'm after. I am trying to manipulate the selected option of a select box. Can someone please explain why this works: $('#some_select_box').click(function() { $('#some_select_box option:selected').remove(); }); but this doesn't: $('#some_select_box').click(function() { $('this option:selected').remove(); }); I just want to use "this" instead of spelling out the id of the select box - can someone point me in the right direction for the correct syntax? It's driving me mad because it looks like it should be really simple. And I'm sure it is to someone, but not me, cos its the end of the day and I'm brain-fried... Any pointers much appreciated. Cheers

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  • Node.js for lua?

    - by Shahbaz
    I've been playing around with node.js (nodejs) for the past few day and it is fantastic. As far as I can tell, lua doesn't have a similar integration of libev and libio which let's one avoid almost any blocking calls and interact with the network and the filesystem in an asynchronous manner. I'm slowly porting my java implementation to nodejs, but I'm shocked that luajit is much faster than v8 JavaScript AND uses far less memory! I imagine writing my server in such an environment (very fast and responsive, very low memory usage, very expressive) will improve my project immensly. Being new to lua, I'm just not sure if such a thing exists. I'll appreciate any pointers. Thanks

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  • Objective-C: Getting the True Class of Classes in Class Clusters

    - by TechZen
    Recently while trying to answer a questions here, I ran some test code to see how Xcode/gdb reported the class of instances in class clusters. (see below) In the past, I've expected to see something like: PrivateClusterClass:PublicSuperClass:NSObject Such as this (which still returns as expected): NSPathStore2:NSString:NSObject ... for a string created with +[NSString pathWithComponents:]. However, with NSSet and subclass the following code: - (void)applicationDidFinishLaunching:(UIApplication *)application { NSSet *s=[NSSet setWithObject:@"setWithObject"]; NSMutableSet *m=[NSMutableSet setWithCapacity:1]; [m addObject:@"Added String"]; NSMutableSet *n = [[NSMutableSet alloc] initWithCapacity:1]; [self showSuperClasses:s]; [self showSuperClasses:m]; [self showSuperClasses:n]; [self showSuperClasses:@"Steve"]; } - (void) showSuperClasses:(id) anObject{ Class cl = [anObject class]; NSString *classDescription = [cl description]; while ([cl superclass]) { cl = [cl superclass]; classDescription = [classDescription stringByAppendingFormat:@":%@", [cl description]]; } NSLog(@"%@ classes=%@",[anObject class], classDescription); } ... outputs: // NSSet *s NSCFSet classes=NSCFSet:NSMutableSet:NSSet:NSObject //NSMutableSet *m NSCFSet classes=NSCFSet:NSMutableSet:NSSet:NSObject //NSMutableSet *n NSCFSet classes=NSCFSet:NSMutableSet:NSSet:NSObject // NSString @"Steve" NSCFString classes=NSCFString:NSMutableString:NSString:NSObject The debugger shows the same class for all Set instances. I know that in the past the Set class cluster did not return like this. What has changed? (I suspect it is a change in the bridge from Core Foundation.) What class cluster report just a generic class e.g. NSCFSet and which report an actual subclass e.g. NSPathStore2? Most importantly, when debugging how do you determine the actual class of a NSSet cluster instance?

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  • WPF RadioButton selected in UI, but seen by code as IsChecked == false

    - by Mike
    I have some radio buttons in a group box. I select the buttons randomly, and all works perfectly from a visual standpoint and also the event handler is called each time a new button is selected. Now I have a dependency property with a callback when the value changes. When in this callback procedure I read the IsChecked value of any button, the value is False, in spite the button is visually selected (they are all false at the same time, strange). The debugger also displays all buttons unchecked. Hu hu, I'm lacking ideas about the reason, after the basic verifications... <GroupBox> <StackPanel> <RadioButton x:Name="btNone" Content="Disconnected" IsChecked="True" Checked="OnSelChecked"/> <RadioButton x:Name="btManual" Content="Manual" Checked="OnSelChecked"/> </StackPanel> </GroupBox> Event handler: private void OnSelChecked(object sender, RoutedEventArgs e) { if (btManual.IsChecked == true) { // is called } } Dependency property: public static readonly DependencyProperty ManualProperty = DependencyProperty.Register("Manual", typeof(Position), typeof(SwitchBox), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender, new PropertyChangedCallback(OnManualChanged))); Dependency property callback: private static void OnManualChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) { SwitchBox box = sender as SwitchBox; if (box.btManual.IsChecked == true) { // never true, why?? } }

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  • Why my inner class DO see a NON static variable?

    - by Roman
    Earlier I had a problem when an inner anonymous class did not see a field of the "outer" class. I needed to make a final variable to make it visible to the inner class. Now I have an opposite situation. In the "outer" class "ClientListener" I use an inner class "Thread" and the "Thread" class I have the "run" method and does see the "earPort" from the "outer" class! Why? import java.io.IOException; import java.net.*; import java.io.BufferedReader; import java.io.InputStreamReader; public class ClientsListener { private int earPort; // Constructor. public ClientsListener(int earPort) { this.earPort = earPort; } public void starListening() { Thread inputStreamsGenerator = new Thread() { public void run() { System.out.println(earPort); try { System.out.println(earPort); ServerSocket listeningSocket = new ServerSocket(earPort); Socket serverSideSocket = listeningSocket.accept(); BufferedReader in = new BufferedReader(new InputStreamReader(serverSideSocket.getInputStream())); } catch (IOException e) { System.out.println(""); } } }; inputStreamsGenerator.start(); } }

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  • Why do bind1st and bind2nd require constant function objects?

    - by rlbond
    So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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  • Storing records in a dropdownlist from DB without using LINQ Data source

    - by user1318369
    I have a website for dance academy where Users can register and add/drop dance classes. In the web page to drop a particular dance, for a particular user, the dropdown displays her registered dances. Now I want to delete one of the dances from the list. So i'll remove the row from the table and also from the dropdownlist. The problem is that everytime the item with the lowest ID (index) is getting deleted, no matter which one the user selects. I think I am storing the DataTextField and DataValueField for the dropdown incorrectly. Can someone please help me out? The code is: private void PopulateDanceDropDown() { var registereddanceList = from dd in context.DANCER_AND_DANCE where dd.UserId == dancerId select new { Text = dd.DanceName, Value = dd.DanceId }; dances.DataSource = registereddanceList; dances.DataTextField = "Text"; dances.DataValueField = "Value"; dances.DataBind(); } protected void dropthedance(object o, EventArgs e) { String strDataValueField = dances.SelectedItem.Value; int danceIDFromDropDown = Convert.ToInt32(strDataValueField); var dancer_dance = from dd in context.DANCER_AND_DANCE where dd.DanceId == danceIDFromDropDown select dd; foreach (var dndd in dancer_dance) { context.DANCER_AND_DANCE.DeleteOnSubmit(dndd); } try { context.SubmitChanges(); } catch (Exception ex) { Console.WriteLine(ex); } PopulateDanceDropDown(); }

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  • how to manually add a cookie to Mechanize state?

    - by fearless_fool
    [I'm working in Ruby, but my question is valid for other languages as well.] I have a Mechanize-driven application. The server I'm talking to sets a cookie using javascript (rather than standard set-cookie), so Mechanize doesn't catch the cookie. I need to pass that cookie back on the next GET request. The good news is that I already know the value of the cookie, but I don't know how to tell Mechanize to include it in my next GET request. Pointers or suggestions are welcome. Thanks in advance. -ff

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  • Design of std::ifstream class

    - by Nawaz
    Those of us who have seen the beauty of STL try to use it as much as possible, and also encourage others to use it wherever we see them using raw pointers and arrays. Scott Meyers have written a whole book on STL, with title Effective STL. Yet what happened to the developers of ifstream that they preferred char* over std::string. I wonder why the first parameter of ifstream::open() is of type const char*, instead of const std::string &. Please have a look at it's signature: void open(const char * filename, ios_base::openmode mode = ios_base::in ); Why this? Why not this: void open(const string & filename, ios_base::openmode mode = ios_base::in ); Is this a serious mistake with the design? Or this design is deliberate? What could be the reason? I don't see any reason why they have preferred char* over std::string. Note we could still pass char* to the latter function that takes std::string. That's not a problem! By the way, I'm aware that ifstream is a typedef, so no comment on my title.:P. It looks short that is why I used it. The actual class template is : template<class _Elem,class _Traits> class basic_ifstream;

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  • Help with Hashmaps in Java

    - by Crystal
    I'm not sure how I use get() to get my information. Looking at my book, they pass the key to get(). I thought that get() returns the object associated with that key looking at the documentation. But I must be doing something wrong here.... Any thoughts? import java.util.*; public class OrganizeThis { /** Add a person to the organizer @param p A person object */ public void add(Person p) { staff.put(p, p.getEmail()); System.out.println("Person " + p + "added"); } /** * Find the person stored in the organizer with the email address. * Note, each person will have a unique email address. * * @param email The person email address you are looking for. * */ public Person findByEmail(String email) { Person aPerson = staff.get(email); return aPerson; } private Map<Person, String> staff = new HashMap<Person, String>(); public static void main(String[] args) { OrganizeThis testObj = new OrganizeThis(); Person person1 = new Person("J", "W", "111-222-3333", "[email protected]"); testObj.add(person1); System.out.println(testObj.findByEmail("[email protected]")); } }

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  • How to get pixel information inside a fragment shader?

    - by user697111
    In my fragment shader I can load a texture, then do this: uniform sampler2D tex; void main(void) { vec4 color = texture2D(tex, gl_TexCoord[0].st); gl_FragColor = color; } That sets the current pixel to color value of texture. I can modify these, etc and it works well. But a few questions. How do I tell "which" pixel I am? For example, say I want to set pixel 100,100 (x,y) to red. Everything else to black. How do I do a : "if currentSelf.Position() == (100,100); then color=red; else color=black?" ? I know how to set colors, but how do I get "my" location? Secondly, how do I get values from a neighbor pixel? I tried this: vec4 nextColor = texture2D(tex, gl_TexCoord[1].st); But not clear what it is returning? if I'm pixel 100,100; how do I get the values from 101,100 or 100,101?

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  • Am I using handlers in the wrong way?

    - by superexsl
    Hey, I've never used HTTP Handlers before, and I've got one working, but I'm not sure if I'm actually using it properly. I have generated a string which will be saved as a CSV file. When the user clicks a button, I want the download dialog box to open so that the user can save the file. What I have works, but I keep reading about modifying the web.config file and I haven't had to do that. My Handler: private string _data; private string _title = "temp"; public void AddData(string data) { _data = data; } public bool IsReusable { get { return false; } } public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/csv"; context.Response.AddHeader("content-disposition", "filename=" + _title + ".csv"); context.Response.Write(_data); context.Response.Flush(); context.Response.Close(); } And this is from the page that allows the user to download: (on button click) string dataToConvert = "MYCSVDATA...."; csvHandler handler = new csvHandler(); handler.AddData(dataToConvert); handler.ProcessRequest(this.Context); This works fine, but no examples I've seen ever instantiate the handler and always seem to modify the web.config. Am I doing something wrong? Thanks

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  • UIImagePickerControllerDelegate Returns Blank "editingInfo" Dictionary Object

    - by Leachy Peachy
    Hi there, I have an iPhone app that calls upon the UIImagePickerController to offer folks a choice between selecting images via the camera or via their photo library on the phone. The problem is that sometimes, (Can't always get it to replicate.), the editingInfo dictionary object that is supposed to be returned by didFinishPickingImage delegate message, comes back blank or (null). Has anyone else seen this before? I am implementing the UIImagePickerControllerDelegate in my .h file and I am correctly implementing the two delegate methods: didFinishPickingImage and imagePickerControllerDidCancel. Any help would be greatly appreciated. Thank you in advance! Here is my code... my .h file: @interface AddPhotoController : UIViewController <UIImagePickerControllerDelegate, UINavigationControllerDelegate> { IBOutlet UIImageView *imageView; IBOutlet UIButton *snapNewPictureButton; IBOutlet UIButton *selectFromPhotoLibraryButton; } @property (nonatomic, retain) UIImageView *imageView; @property (nonatomic, retain) UIButton *snapNewPictureButton; @property (nonatomic, retain) UIButton * selectFromPhotoLibraryButton; my .m file: @implementation AddPhotoController @synthesize imageView, snapNewPictureButton, selectFromPhotoLibraryButton; - (IBAction)getCameraPicture:(id)sender { UIImagePickerController *picker = [[UIImagePickerController alloc] init]; picker.delegate = self; picker.sourceType = UIImagePickerControllerSourceTypeCamera; picker.allowsImageEditing = YES; [self presentModalViewController:picker animated:YES]; [picker release]; } - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo { NSLog(@"Image Meta Info.: %@",editingInfo); UIImage *selectedImage = image; imageView.image = selectedImage; self._havePictureData = YES; [self.useThisPhotoButton setEnabled:YES]; [picker dismissModalViewControllerAnimated:YES]; } - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker { [picker dismissModalViewControllerAnimated:YES]; }

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  • How to get rid of gap when I add my custom UIViewController to window?

    - by wgpubs
    I'm getting this gap at the bottom of my window after I add the view of a custom UIViewController. The gap goes away as the view is shifted down after I move to another view and then back. Here is the code in the app delegate: - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after application launch CustomViewController *gvc = [[CustomViewController alloc] init]; self.customViewController = gvc; [gvc release]; [window addSubview:customViewController.view]; [window makeKeyAndVisible]; } "CustomViewController" is used as a root view controller to simply coordinate which other UIViewControllers to display. As such I simply set its view = to that of the first ViewController's view needed like so: - (void)loadView { UIView *v = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)]; self.view = v; [v release]; // Add the HomeViewController to the top of the stack MainViewController *mvc = [[MainViewController alloc] initWithNibName:@"MainView" bundle:nil]; mvc.delegate = self; self.mainViewController = mvc; [mvc release]; [self.view addSubview:self.mainViewController.view]; } I've tried a bunch of things including what you see here with no luck. Any ideas? thanks

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  • iOS MapKit: Selected MKAnnotation coordinates.

    - by Oh Danny Boy
    Using the code at the following tutorial, http://www.zenbrains.com/blog/en/2010/05/detectar-cuando-se-selecciona-una-anotacion-mkannotation-en-mapa-mkmapview/, I was able to add an observer to each MKAnnotation and receive a notification of selected/deselected states. I am attempting to add a UIView on top of the selection annotation to display relevant information about the location. This information cannot be conveyed in the 2 lines allowed (Title/Subtitle) for the pin's callout. - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { Annotation *a = (Annotation *)object; // Alternatively attempted using: //Annotation *a = (Annotation *)[mapView.selectedAnnotations objectAtIndex:0]; NSString *action = (NSString *)context; if ([action isEqualToString:ANNOTATION_SELECTED_DESELECTED]) { BOOL annotationSelected = [[change valueForKey:@"new"] boolValue]; if (annotationSelected) { // Actions when annotation selected CGPoint origin = a.frame.origin; NSLog(@"origin (%f, %f) ", origin.x, origin.y); // Test UIView *v = [[UIView alloc] init]; [v setBackgroundColor:[UIColor orangeColor]]; [v setFrame:CGRectMake(origin.x, origin.y , 300, 300)]; [self.view addSubview:v]; [v release]; }else { // Accions when annotation deselected } } } Results using Annotation *a = (Annotation *)object origin (154373.000000, 197135.000000) origin (154394.000000, 197152.000000) origin (154445.000000, 197011.000000) Results using Annotation *a = (Annotation *)[mapView.selectedAnnotations objectAtIndex:0]; origin (0.000000, 0.000000) origin (0.000000, 0.000000) origin (0.000000, 0.000000) The numbers are large. They are not relative to the view (1024 x 768). I believe they are relative to the entire map. How would I be able to detect the exact coordinates relative to the entire view so that I can appropriately position my view?

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  • volatile keyword seems to be useless?

    - by Finbarr
    import java.util.concurrent.CountDownLatch; import java.util.concurrent.atomic.AtomicInteger; public class Main implements Runnable { private final CountDownLatch cdl1 = new CountDownLatch(NUM_THREADS); private volatile int bar = 0; private AtomicInteger count = new AtomicInteger(0); private static final int NUM_THREADS = 25; public static void main(String[] args) { Main main = new Main(); for(int i = 0; i < NUM_THREADS; i++) new Thread(main).start(); } public void run() { int i = count.incrementAndGet(); cdl1.countDown(); try { cdl1.await(); } catch (InterruptedException e1) { e1.printStackTrace(); } bar = i; if(bar != i) System.out.println("Bar not equal to i"); else System.out.println("Bar equal to i"); } } Each Thread enters the run method and acquires a unique, thread confined, int variable i by getting a value from the AtomicInteger called count. Each Thread then awaits the CountDownLatch called cdl1 (when the last Thread reaches the latch, all Threads are released). When the latch is released each thread attempts to assign their confined i value to the shared, volatile, int called bar. I would expect every Thread except one to print out "Bar not equal to i", but every Thread prints "Bar equal to i". Eh, wtf does volatile actually do if not this?

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  • How to make safe frequent DataSource switches for AbstractRoutingDataSource?

    - by serg555
    I implemented Dynamic DataSource Routing for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query. Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use: public class CustomerContextHolder { private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>(); public static void setCustomerType(CustomerType customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType); } public static CustomerType getCustomerType() { return (CustomerType) contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } } It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel: CustomerContextHolder.setCustomerType(CustomerType.GOLD); //<another user will switch customer type here to CustomerType.SILVER in another request> List<Item> goldItems = catalog.getItems(); Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true. How to make sure that nobody else will switch datasource until I run required query for current user? Thanks.

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  • LINQ to Sql: Insert instead of Update

    - by Christina Mayers
    I am stuck with this problems for a long time now. Everything I try to do is insert a row in my DB if it's new information - if not update the existing one. I've updated many entities in my life before - but what's wrong with this code is beyond me (probably something pretty basic) I guess I can't see the wood for the trees... private Models.databaseDataContext db = new Models.databaseDataContext(); internal void StoreInformations(IEnumerable<EntityType> iEnumerable) { foreach (EntityType item in iEnumerable) { EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault(); if (type == null) { db.EntityType.InsertOnSubmit(item); } else { type.Date = item.Date; type.LastUpdate = DateTime.Now(); type.End = item.End; } } } internal void Save() { db.SubmitChanges(); } Edit: just checked the ChangeSet, there are no updates only inserts. For now I've settled with foreach (EntityType item in iEnumerable) { EntityType type = db.EntityType.Where(t => t.Room == item.Room).FirstOrDefault(); if (type != null) { db.Exams.DeleteOnSubmit(type); } db.EntityType.InsertOnSubmit(item); } but I'd love to do updates and lose these unnecessary delete statements.

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  • Type result with Ternary operator in C#

    - by Vaccano
    I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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  • Serializing QGraphicsScene contents

    - by Rob
    I am using the Qt QGraphicsScene class, adding pre-defined items such as QGraphicsRectItem, QGraphicsLineItem, etc. and I want to serialize the scene contents to disk. However, the base QGraphicsItem class (that the other items I use derive from) doesn't support serialization so I need to roll my own code. The problem is that all access to these objects is via a base QGraphicsItem pointer, so the serialization code I have is horrible: QGraphicsScene* scene = new QGraphicsScene; scene->addRect(QRectF(0, 0, 100, 100)); scene->addLine(QLineF(0, 0, 100, 100)); ... QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { if (item->type() == QGraphicsRectItem::Type) { QGraphicsRectItem* rect = qgraphicsitem_cast<QGraphicsRectItem*>(item); // Access QGraphicsRectItem members here } else if (item->type() == QGraphicsLineItem::Type) { QGraphicsLineItem* line = qgraphicsitem_cast<QGraphicsLineItem*>(item); // Access QGraphicsLineItem members here } ... } This is not good code IMHO. So, instead I could create an ABC class like this: class Item { public: virtual void serialize(QDataStream& strm, int version) = 0; }; class Rect : public QGraphicsRectItem, public Item { public: void serialize(QDataStream& strm, int version) { // Serialize this object } ... }; I can then add Rect objects using QGraphicsScene::addItem(new Rect(,,,)); But this doesn't really help me as the following will crash: QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { Item* myitem = reinterpret_class<Item*>(item); myitem->serialize(...) // FAIL } Any way I can make this work?

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  • Comparing two images from the clipboard class

    - by VeXe
    In a C# winform app. I'm writing a Clipboard log manager that logs test to a log file, (everytime a Ctrl+c/x is pressed the copied/cut text gets appended to the file) I also did the same for images, that is, if you press "prtScreen", the screen shot you took will also go to a folder. I do that by using a timer, inside I have something which 'looks' like this: if (Clipboard.ContainsImage()) { if (IsClipboardUpdated()) { LogData(); UpdateLastClipboardData(); } } This is how the rest of the methods look like: public void UpdateLastClipboardData() { // ... other updates LastClipboardImage = Clipboard.GetImage(); } // This is how I determine if there's a new image in the clipboard... public bool IsClipboardUpdated() { return (LastClipboardImage != Clipboard.GetImage()); } public void LogData() { Clipboard.GetImage().Save(ImagesLogFolder + "\\Image" + now_hours + "_" + now_mins + "_" + now_secs + ".jpg"); } The problem is: inside the update method, "LastClipboardImage != Clipboard.GetImage()" is always returning true! I even did the following inside the update method: Image img1 = Clipboard.GetImage(); Image img2 = Clipboard.GetImage(); Image img3 = img2; bool b1 = img1 == img2; // this returned false. WHY?? bool b2 = img3 == img2; // this returned true. Makes sense. Please help, the comparison isn't working... why?

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