writing global listener

Question

I want the active window (i.e JFrame ot JDialog) to receive specific keyEvent so that whereever the focusing this keyevent is handling by the window such as ALT+F4 if you press it wherever the focusing the active window will close,I try to override postprocesskeyEvent but it doesn't work fine

Answer 1

You can add a global event listener to you application using the addAWTEventListener() method in java.awt.Toolkit.

http://java.sun.com/javase/6/docs/api/java/awt/Toolkit.html#addAWTEventListener%28java.awt.event.AWTEventListener,%20long%29

You will need to choose which type of events you want to receive with the event mask when you add the listener.

For example:

// Then on startup register.
AWTEventListener myGlobalKeyListener = new MyGlobalKeyListener();

Toolkey.getDefaultToolkit().addAWTEventListener(myGlobalKeyListener, AWTEvent.KEY_EVENT_MASK);

If you are trying to stop windows from shutting down your application when the user presses ALT-F4 then an event handler will not help you. I belive the operating system handles this by sending SIGTERM to the application. Java does not receive the KeyEvent for this.

Answer 2

The standard approach for intercepting KeyStrokes when using Swing is to use Key Bindings. Although as mentioned earlier this still won't work for Alt+F4.

If you are trying to prevent Alt+F4 from closing the window, then you need to use the setDefaltCloseOperation(...) method to do nothing. Closing an Application gives more information on this approach.