Update JFrame via another Thread

Question

Hello,
I have a JFrame with a JProgressBar, and I need to see the JProgressBar fill as some operation executes. In that JFrame there's a public method that increments the JProgressBar. This serves as a GUI to another class. That other class receives, as an argument, the JFrame, in order to be able to call that public method to increment the JProgressBar.
Something like:
public class Worker{
   public Worker(JFrame jf){
      this.frame = jf;
   public doWork(){
      instruction1;
      frame.updateProgressBar();
      instruction2;
      frame.updateProgressBar();
}This has a major problem: the JFrame's graphics won't be updated (you won't see the progress bar filling during the operation). So I made a class to run the Worker on a Thread, that looks something like:
public class WorkerThread extends Thread{
   public WorkerThread (Worker w){
      this.worker= w;
   public void run(){
      w.doWork();    
}This got the problem solved, the JProgressBar is now correctly updated. But it created a new problem: I need the JFrame to wait for the WorkerThread to finish, and that's what I'm having real trouble with:
public class GUI extends JFrame{
   private worker = new Worker();
   void someButtonPressed(...){
      WorkerThread wt = new WorkerThread(worker);
      wt.start();
      System.out.println("I don't want to see this until the Thread finishes");
}If I leave this as is, I'll see the text before the Thread finishes.
So I added "wait()" between the last two instructions, and a "notify()" as the last instruction of the run() method on WorkerThread. Unfortunately, this gives me two exceptions (java.lang.IllegalMonitorStateException: current thread not owner), one when I call wait() and another when I call notify(). If I make the two methods that call wait() and notify() synchronized, the JFrame's graphics won't update correctly (back to the initial problem).
Any suggestions? Sorry for the long post, and thanx in advance! :)

Answer 1

I don't really understand why you are using two JFrames.
Typically in an application you have a single main JFrame. Whenever you need additional information you would create and display a "modal" JDialog. A modal JDialog prevents the JFrame from receiving any events. So in your example the progress bar should be added the dialog. When the long running task is finished you close the dialog an execution continues back in your main JFrame.