How is a JDialog's owner still updating it's UI even when it's EDT is blocked?

Asked Nov 08 '13 at 03:16

Active Nov 08 '13 at 03:18

Viewed 82 times

I have the following example code:

public class MainWindow extends JFrame implements ActionListener {
    public MainWindow() {
       JButton openButton = new JButton('Open');
       openButton.addActionListener(this);
       add(openButton);
    }

    public void actionPerformed(ActionEvent e) {
       // Create and show a modal dialog.
       JDialog dialog = new JDialog(this, true);
       dialog.setVisible(true);
    }
}

When I click the openButton it calls actionPerformed(ActionEvent e) on the event dispatch thread and dialog.setVisible(true) blocks it.

But with more sophisticated frames I notice that they still update their UI from non user generated events such as a Timer action.

In any other case that I block the EDT my UI completely hangs, but when dialog.setVisible(true) blocks the EDT the owner's UI continues to update.

So my question is how does this work?

asked Nov 08 '13 at 03:16

Benjamin Albert

3

It creates it's own event queue – MadProgrammer Nov 08 '13 at 03:17
@ MadProgrammer Thank you for your response, but can you be more specific with "it" and how does that make the owner respond to events? – Benjamin Albert Nov 08 '13 at 03:24
Your Timer was started before the modal dialog was shown, correct? – Hovercraft Full Of Eels Nov 08 '13 at 03:42
@Hovercraft Full Of Eels yes – Benjamin Albert Nov 08 '13 at 03:56
3

Basically, the dialog creates it's own Event Queue and filters the events coming through it. You can open the source code and take a look – MadProgrammer Nov 08 '13 at 03:57
See also this related [example](http://stackoverflow.com/a/18728637/230513). – trashgod Nov 08 '13 at 04:26
its about good practicies to delay pack(); and setVisible(true); into invokeLater – mKorbel Nov 08 '13 at 06:40

How is a JDialog's owner still updating it's UI even when it's EDT is blocked?

0 Answers0