Question

What I want to achieve is that

• In a certain state, a class should automatically hide dialogs displayed by other classes
• The hidden dialogs should be displayed when state of program changes

Problem:

• This does not work with JOptionPanes
• The JOptionPanes are hidden and displayed again, but then they are automatically closed, so I only see them again for part of a second

I used the following approach:

public static void main(String[] args) {


    Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {

        public void eventDispatched(AWTEvent event) {
            WindowEvent windowEvent = ((WindowEvent) event);
            System.out.println(System.currentTimeMillis() + " " + windowEvent);
            switch (windowEvent.getID()) {
            case WindowEvent.WINDOW_OPENED:
                System.out.println("Hiding");
                windowEvent.getComponent().setVisible(false);
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("Showing");
                windowEvent.getComponent().setVisible(true);
                break;
            }
        }


    }, AWTEvent.WINDOW_EVENT_MASK + AWTEvent.WINDOW_STATE_EVENT_MASK);

    JOptionPane.showMessageDialog(null,
            "Eggs are not supposed to be green.",
            "Inane custom dialog",
            JOptionPane.INFORMATION_MESSAGE);
}

It produces the following output:

1347602481337 java.awt.event.WindowEvent[WINDOW_ACTIVATED,opposite=null,oldState=0,newState=0] 
on dialog0
1347602481337 java.awt.event.WindowEvent[WINDOW_GAINED_FOCUS,opposite=null,oldState=0,newState=0] on dialog0
1347602481337 java.awt.event.WindowEvent[WINDOW_OPENED,opposite=null,oldState=0,newState=0] on dialog0
Hiding
Showing
1347602486377 java.awt.event.WindowEvent[WINDOW_LOST_FOCUS,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_DEACTIVATED,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_ACTIVATED,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_GAINED_FOCUS,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_LOST_FOCUS,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_DEACTIVATED,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_CLOSED,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_CLOSED,opposite=null,oldState=0,newState=0] on dialog0
1347602486377 java.awt.event.WindowEvent[WINDOW_CLOSED,opposite=null,oldState=0,newState=0] on frame0

My question is, what I did to wrong? Is this per design or do I make an error, do I use the classes the wrong way? If yes, what would be the correct way?

Answer 1

What you did wrong is sleeping on the Event Dispatch Thread:

windowEvent.getComponent().setVisible(false);
try {
  Thread.sleep(5000);
} catch (InterruptedException e) {
  e.printStackTrace();
}
System.out.println("Showing");
windowEvent.getComponent().setVisible(true);

By blocking the EDT for 5 seconds, nothing can get repainted. Use a Timer instead.

See the Concurrency in Swing tutorial for more information.