ContentPane not rendering in threaded JDialog

Question

I want to popup a small dialog whilst my main thread is executing telling the user to be patient.
So, I create JDialog that implements Runnable.
public class TheSplash extends JDialog implements Runnable
public TheSplash(Frame f) {
    super(f, true);
    setTitle("blabla");
    JPanel p = new JPanel();
    JLabel l = new JLabel("text");
    p.add(l);
    getContentPane().add(p, BorderLayout.CENTER);
    setSize(150, 100);
    setLocationRelativeTo(f);
public void run() {
    setVisible(true);
}Now, in my main thread (Event Despatch Thread) I do
final TheSplash splash = new TheSplash(someFrameInstance);
Thread t = new Thread(splash);
t.start();
// lengthy processes happen here
splash.setVisible(false);
splash.dispose();
// more stuffNow, the dialog displays and disappears at the required times, but the only things rendered on screen are the actual dialog and title, but not the contentPane of the TheSplash instance.
What gives? I tried forcing it to repaint right after completion, doing a step-by-step debug through the code, the code runs through the entire TheSplash constructor as expected, without errors...
Any help appreciated....

Answer 1

Hi,
you have to put the setVisible(true) method in the EventDispatchingThread. At the moment it is not in the E-Thread because you explicitly start a new Thread Thread t = new Thread(splash);Change this to
SwingUtilities.invokeLater(splash);and run the lengthy process in a separate Thread (not the E-Thread) and join() this thread to get informed of the end.
Thread t = new Thread(new Runnable() {
  public void run() {
     // lengthy process
t.start();
t.join();All GUI-things in the lengthy process must be dispatched to the E-Thread.
Ulrich