Question

Hi noticed some code in our application when I first started Java programming. I had noticed it created a dialog from a separate thread, but never batted an eye lid as it ‘seemed to work’. I then wrapped this method up through my code to display dialogs.

This is as follows:

public class DialogModalVisibleThread
        extends Thread {
    private JDialog jDialog;
    public DialogModalVisibleThread(JDialog dialog, String dialogName) {
        this.setName("Set " + dialogName + " Visable");
        jDialog = dialog;
    }

    @Override
    public void run() {
       jDialog.setVisible(true);
       jDialog.requestFocus();
    }
}

Usage:

WarnUserDifferenceDialog dialog = new WarnUserDifferenceDialog( _tableDifferenceCache.size() );
DialogModalVisibleThread dmvt = new DialogModalVisibleThread( dialog, "Warn User About Report Diffs");
dmvt.start();

Now, as far as I am now aware, you should never create or modify swing components from a separate thread. All updates must be carried out on the Event Dispatch Thread. Surely this applies to the above code?

EDT on WikiPedia

However, the above code has worked.

But lately, there have been countless repaint issues. For example, click on a JButton which then calls DialogModalVisibleThread to display a dialog. It caused buttons alongside the clicked button not to redraw properly.

The repaint problem is more frequent on my machine and not the other developers machine. The other developer has a laptop with his desktop extended onto a 21″ monitor – the monitor being his main display. He is running Windows 7 with Java version 1.6.0_27.

I am running on a laptop with Windows 7 and Java version 1.6.0_24. I have 2 additional monitors with my desktop extended onto both.

In the meantime I am going to upgrade to Java 1.6 update 27.

I wondered if the above code could cause repaint problems or are there any other people out there with related paint issues?

Are there any easy ways to diagnose these problems?

Thanks

Answer 1

So, you’re breaking a rule, having problems, and wondering if these problems could be cause by the fact that you broke the rule. The answer is Yes. Respect the rules!

To detect the violations, you might be interested by the following page: http://weblogs.java.net/blog/2006/02/16/debugging-swing-final-summary