How to update/paint JProgressBar while Swing is loaded building the GUI

Question

I have a GUI which is quite heavy to build/initialize on the platform on which it runs.. Therefore I want to update progress while it initializes..

I have a small undecorated JDialog containing a JLabel and a JProgressBar which I want to update at specific places during initialization, however, because the event dispatch thead (as per Swing rules) is used to build/initialize the GUI, the progress is of course not updated until the EDT is idle again (i.e. initialization is finished)..

The JProgressBar I have gotten to redraw using "paintImmediately", but I can't seem to make it work properly for the JLabel and the dialog itself.. Is there any simple recommended/proven method to accomplish this?

cheers...

EDIT: Adding an example of what it is I'm trying to do; greatly simplified, of course.

private JLabel progressLabel;
private JProgressBar progressBar;

public static int main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            showProgressDialog();
            progressLabel.setText("construct 1");

            constructSomeHeavyGUI();

            progressLabel.setText("construct 2");
            progressBar.setValue(33);

            constructSomeMoreHeavyGUI();

            progressLabel.setText("construct 3");
            progressBar.setValue(67);

            constructEvenMoreHeavyGUI();

            progressLabel.setText("done");
            progressBar.setValue(100);

            hideProgressDialog();

            showHeavyGUI();

        }
    });
}

the repaints caused by the calls to progressBar.setValue()/progressLabel.setText() above will of course get queued as long as the EDT is busy and result in a repaint after we are all done instead of updating along the way..

Answer 1

It's possible that constructSome*HeavyGUI() really takes long enough to matter, but it's more likely that filling in the data model(s) is the problem. Instead, construct and show the empty GUI elements and launch one or more SwingWorker instances to marshal each element's data. There are related examples here and here.

Addendum: If the problem is instantiating components, and not loading data models, you can chain the calls to invokeLater(), as suggested in a comment below. If you're instantiating that many components, consider the flyweight pattern. JTable is a familiar example.