JProgressBar inside JDialogBox doesn't show up.

Question

Hi,
I have a problem and kind of stuck.
Here is the scenario.....
Inside my actionPerformed method I create an instance of a class that extends java.lang.Thread and inside this class run method I create an instance of another class that extends JDialog that contains a JProgressBar. Now when a user clicks a button on the main application window the actionPerformed gets executed and it shows a JProgressBar and then continues the execution of the actionPerformed method while the JProgressBar keeps on updating the status. But the problem is that the JDialog shows up but the JProgressBar inside it doesn't even show. here is the code snippet I am using
public void actionPerformed(ActionEvent e)
//some code here
//class extends Thread and creates JDialog with JProgressBar in it
//JDialogBox with JProgressBar in it shows here
t = new ProgressThread();
t.start();
//some other code I do some other processing
//here I am hidding and destroying the JProgressBar
//inside the reset method I hide the JDialog and set it to null
t.reset();
//some more code
} //end of actionPerform
Now my problem is that JDialogBox does pop-up but the JProgressBar in it doesn't show. Any ideas what I am doing wrong. I even tried to create the instance of JDialog directly instead of using a separate Thread but it didn't work either.
Thanks for any help

Answer 1

The point being, AWT and Swing are, in general, not thread-safe.
You must not do anything that modifies the appearance of any visible Swing component, such as JProgressBar, from your thread. This must be done in the AWT Event Dispatch Thread. But when the components are not visible, like when you are building your GUI and haven't set it to visible yet, this doesn't apply.
What I do, when my threads need to update the GUI, is to create a Runnable to do it, then queue that to the AWT Event Dispatch Thread for execution by calling SwingUtilities.invokeLater(). Other people use this SwingWorker class.
Note that event listener methods are called in the AWT Event Dispatch Thread, so you need to worry about this only in your own thread.
It is said there are some Swing components that are thread-safe. Given the typical use of JProgressBar, too bad it isn't one of them.