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ClassCastException with JDialog and Thread

Answer 1

A:

All updates to Swing components should be done on the Event Dispatch Thread (EDT).

In your Thread you attempt to pack() the dialog every second. This code is NOT executing on the EDT.

Try using a SwingUtilities.invokeLater(...) to do the pack().

Or maybe a SwingWorker should be used instead of the Thread. Read the section from the Swing tutorial on Concurrency for more information.

Or maybe even a better approach is to start a Swing Timer to schedule closing of the dialog. When the Timer fires the code is automatically executed on the EDT. The Swing tutorial also has a section on using Timers.

camickr 2010-06-03 14:25:21

Answer 2

+1 A:

Doing UI modifications in a Thread other than Swing's EventDispatchThread is strongly discouraged, as it can and will lead to weird side effects (just as the one you encountered).

Immagine the UI is about to repaint itself (and layout stuff) and you just interfer by changing parts of the UI at the same time using another thread. In such a situation chaos is verly likely to ensue.

For details see the Java Tutorials Lesson Concurrency in Swing

The correct way to deal with this is to have the background thread do any work that is not UI related, and schedule a UI update job in the EventDispatchThread (which will execute the job between handling events).

Example:

    Thread t = new Thread() {

        public void run () {

            // do background work

            SwingUtilities.invokeLater(new Runnable() {

                public void run () {
                    // update UI parts
                }
            });
        }
    };
    t.start();

SwingUtilities.invokeLater(Runnnable) will schedule a Runnable for later execution, whereas SwingUtilities.invokeAndWait(Runnnable) will schedule a Runnable and wait until it has been executed.

Peter Walser 2010-06-03 14:37:33

Answer 3

A:

arcamax 2010-06-03 16:16:54

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ClassCastException with JDialog and Thread

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