Problem with painting/threads/ProgressMonitor

Question

Hello,
I'll try to be clear, ask me anything if it isn't. I have two threads, one that downloads some selected webpages, and the other that reads them. In the thread that reads, there is a ProgressMonitor object, which indicate how many webpages have been read.
I created a JUnit test which works as expected. One thread downloads, the other reads and a nice little progress monitor appears and everything works.
I transfered the code (the part of the code starting the thread that reads, which starts the thread that downloads) into the main application. The threads are working and the ProgressMonitor appears, but it does not draw the components (there is no label, progress bar, button etc...). I can't seem to find the problem. I think it is caused by the threads or synchronized methods, I am not sure as I am no expert with threads. Once the threads have finished running, the components of the ProgressMonitor appears. So I guess that the threads are blocking the (re)painting of the application, but I can't figure why. Im using Thread.yield() quite often. Priorities problem ? Here some parts of the code :
JUnit Test code :
     public synchronized void testHarvest() {
          JFrame frame = new JFrame("Super");
          frame.setVisible(true);
          Harvester harvester = new Harvester(
                    frame,
                    new Rule());
          Thread harvest = new Thread(harvester);
          harvest.start();
          try {
               harvest.join();
          } catch (InterruptedException ie) {}
...Main application :
Code:
public class Gui extends JFrame implements ComponentListener {
   private static JFrame mMotherFrame = null;
    public Gui() {
        mMotherFrame = this;
    private class GuiActionRealize {
          public synchronized void getFromWeb() {
               Harvester harvester = new Harvester(
                         mMotherFrame,
                         new Rule());
               Thread harvest = new Thread(harvester);
               harvest.start();               
               try {                    
                    harvest.join();
               } catch (InterruptedException ie) {}
}Harvester :
Code:
public class Harvester implements Runnable {
  private JFrame mMotherFrame;
  private ProgressMonitor mMonitor;
public Harvester(JFrame owner, IRule subjectRule) {
   mMotherFrame = owner;
    public void find() {
    mMonitor = new ProgressMonitor(mMotherFrame, "Downloading from the Internet.", "", 1, mAcceptedURLs.size());
     mMonitor.setMillisToDecideToPopup(0);
     mMonitor.setMillisToPopup(0);
public void run() {
  find();
  mHarvested = harvest();
  mFinished = true;
  Thread.yield();
public List harvest() {
  download = new DownloadThread(this, mAcceptedURLs);
  Thread downthread = new Thread(download);
  downthread.start(); int i = 0;
  while (!mMonitor.isCanceled()) {
      while (download.getDownloadedDocuments().isEmpty()) {
           try {
                   Thread.yield();
                   Thread.sleep(300);
            } catch (InterruptedException ie) {}
       mMonitor.setNote("Downloading decision " + i);
       mMonitor.setProgress(mMonitor.getMinimum()+ ++i);
       } // end while(!cancel)
       download.kill();
       return mHarvested;
}I'm very puzzled by the fact that it worked in the JUnit Case and not in the application.
I can see that the thread that is responsible for drawing components is not doing his job, since that the mother frame (Gui class) is not being repainted while the harvest/download threads are working. That's not the case in the JUnit case, where the frame is being repainted and everything is fine. This is the only place in the application that I'm using threads/runnable objects.
I also tried making the Gui class a thread by implementing the Runnable interface, and creating the run method with only a repaint() statement.
And I tried setting the priority of the harvest thread to the minimum. No luck.
If you need more info/code, let me know, Ill try to give as much info as I can.
Thank you

Answer 1

Why are you painting the values yourself? Why don't you just add the selected values to a JList, or create a container with a GridLayout and add a JLabel with the new text to the container.
Every time you call the paintComponent() method the painting gets done from scratch so you would need to keep a List of selected items and repaint each item every time. Maybe this [url http://forum.java.sun.com/thread.jsp?forum=57&thread=304939]example will give you ideas.