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JFrame.setDefaultCloseOperation() not behaving properly?

 
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shimniok



Joined: 11 Oct 2010
Posts: 8
Location: Colorado
PostPosted: Wed Oct 20, 2010 4:35 am    Post subject: JFrame.setDefaultCloseOperation() not behaving properly? Reply with quote
Hi, hoping the gurus here may be able to help this newb.

I'm attempting to intercept a close window event in my Swing desktop application (testing on Windows at the moment) so I can prompt the user to save a file (yes/no/cancel). The code that should work, doesn't. What am I goofing up?

Code:
public class WheelEncoderGeneratorView extends FrameView {

    public WheelEncoderGeneratorView(SingleFrameApplication app) {
        super(app);

        System.out.println("Initializing components...");
        initComponents();
        registerForMacOSXEvents(); // OSX-specific setup

        // Handle window close event
        getFrame().setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
        getFrame().addWindowListener(new CloseListener());
//...
        System.out.println("Done with View initialization...");
    }

//...

    private class CloseListener extends WindowAdapter {
        @Override
        public void windowClosing(WindowEvent event) {
            System.out.println("windowClosing() -- enter");
            if (promptSaveFirst()) {
                System.out.println("windowClosing() -- disposing of window");
                getFrame().dispose();
            } else {
                System.out.println("windowClosing() -- cancelling close");
            }
            System.out.println("windowClosing() -- exit");
            //System.exit(0);
        }
    }
}


Output from running the app, then clicking the close box, then selecting "Cancel" is:

Quote:
Done with View initialization...
windowClosing() -- enter
promptSaveFirst() -- return false // indicates a 'cancel' was selected
windowClosing() -- cancelling close
windowClosing() -- exit


In short, the logic is right and the code is taking the right path for canceling the close action. But the app window closes and the process terminates anyway. The setDefaultCloseOperation with DO_NOTHING_ON_CLOSE isn't behaving like I expected.

I *thought* what was supposed to happen was... nothing. The app should stay running unless I explicitly call System.exit() or dispose() right? I'm not calling either. And the app still closes / terminates.

I'm I calling setDefaultCloseOperation() on the wrong object?

Thanks in advance,

Michael
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shimniok



Joined: 11 Oct 2010
Posts: 8
Location: Colorado
PostPosted: Thu Oct 21, 2010 4:27 am    Post subject: Reply with quote
PS: Same incorrect behavior on OS X ...

Makes me think that I am setting default close operation on the wrong thing or in the wrong way... hmmm.
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shimniok



Joined: 11 Oct 2010
Posts: 8
Location: Colorado
PostPosted: Thu Oct 21, 2010 6:17 am    Post subject: Reply with quote
If I include this field in the FrameView class, then I get the correct DO_NOTHING_ON_CLOSE behavior. At least on OSX (haven't tested win yet).

Code:
    private JFrame mainFrame = WheelEncoderGeneratorApp.getApplication().getMainFrame();


The variable is unused. Yet if I remove it or replace it with, say, this.getFrame(), the DO_NOTHING_ON_CLOSE behavior breaks.

I find this utterly bizarre and nonsensical.
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Zelig



Joined: 04 Apr 2009
Posts: 64
Location: FRANCE
PostPosted: Fri Oct 22, 2010 10:35 am    Post subject: Reply with quote
Hello,

You shouldn't try to prevent the windows from closing in the "close" function. In the FrameView class, you have a function called "CanExit".

Any test which could lead to resuming the application should be written here. This method returns a boolean, true if the application is supposed to close or false if the application should go on running.
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shimniok



Joined: 11 Oct 2010
Posts: 8
Location: Colorado
PostPosted: Fri Oct 22, 2010 4:32 pm    Post subject: Reply with quote
@Zelig: Great tip, thanks! Did a little searching and found this useful explanation:

http://forums.sun.com/thread.jspa?messageID=10228903

See post 12 in the link above. I implemented mine a little differently. I kept all the UI stuff in the View and simply called quit() on it from within the exit listener. That is...

Code:
public class WheelEncoderGeneratorApp extends SingleFrameApplication implements Application.ExitListener
{
    protected WheelEncoderGeneratorView view;

    /**
     * At startup create and show the main frame of the application.
     */
    @Override protected void startup() {
        addExitListener(this);
        show(view = new WheelEncoderGeneratorView(this));
    }

    @Override public boolean canExit(java.util.EventObject e) {
        System.out.println("WheelEncoderGeneratorApp.canExit(): calling view.quit()");
        return view.quit();
    }

    @Override public void willExit(java.util.EventObject e) {
    }
// ...



And then:

Code:
public class WheelEncoderGeneratorView extends FrameView {
//...
    public boolean quit()
    {
        return promptSaveFirst();
    }
//...


I had to first disable the the previous solution's addWindowListener() and setDefaultCloseOperation() calls.

I'm still not sure why the previous solution only worked when declaring that private instance variable with the call to myApp.getApplication().getMainFrame() ... I really don't like inexplicable fixes of that sort, y'know??

Anyway the canExit() bit works great on Windows.

EDIT: works perfectly on OSX, too.

Thanks again!
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shimniok



Joined: 11 Oct 2010
Posts: 8
Location: Colorado
PostPosted: Fri Oct 29, 2010 4:41 pm    Post subject: Reply with quote
Here's a hint as to why I was seeing bizarre behavior with calling: WheelEncoderGeneratorApp.getApplication().getMainFrame();

http://markmail.org/message/4no3q2jc46ldgs6c
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