Problems updating gui in JApplet

[Marte J.]

I have a JApplet with a JPanel with another JPanel � TreePanel � containing a JScrollPane with a JTree.
When init() is run in MyApplet, _treePanel is initiated with a JTree, with test data hardcoded in TreePanel�s constructor. I want the tree to change every time a thread loops, by calling method _treePanel.updateResultTree(root) from the thread, with a new root. To test this, I have hardcoded a new tree content in the thread to pass to the TreePanel. In method updateResultTree(root), I remove the existing JTree from JScrollPane and add a new JTree to it, with the new root. Then I repaint the JScrollPane.
When I run the applet, the initial tree is displayed, but it is not updated with the new JTree for the first thread loop as expected. How is the gui in a JApplet refreshed/updated?? Will SwingWoker update the gui automatically without forcing repaint()?
Please help! Thanks in advance!

MyApplet
________________________________

  
public class MyApplet extends JApplet {
private TreePanel _treePanel;
private UpdateHandler _updateHandler;
private Thread _updateThread;
public void init() {
    super.init();
    _treePanel = new TreePanel();
    // Updating thread
    _updateHandler = new UpdateHandler();
    _updateThread = new Thread(_updateHandler);
    _updateThread.start();
    // Initialize gui 
    JPanel bigPanel = new JPanel();
    bigPanel.setLayout(new BoxLayout(bigPanel, BoxLayout.X_AXIS));           
    getContentPane().add(bigPanel, BorderLayout.CENTER);    
    _treePanel = new JPanel();
    bigPanels.add(_treePanel);
}
// Updates the GUI every X seconds
private class UpdateHandler implements Runnable {
    public final static int UPDATE_INTERVAL = 10;
    public UpdateHandler() { }
    public void run() {
      try {
_displayResults();
      } catch (InterruptedException ie) {
      }
  }
  private synchronized void _ displayResults () throws InterruptedException {
      while(true) {
         // Resolve a new DefaultMutableTreeNode object as root to be updated in GUI
         // (For test)
        DefaultMutableTreeNode root = new DefaultMutableTreeNode(new Result("Root"));
        DefaultMutableTreeNode child_1 = new DefaultMutableTreeNode(new Result("Result X"));
        DefaultMutableTreeNode child_2 = new DefaultMutableTreeNode(new Result("Result Y"));
        DefaultMutableTreeNode child_11 = new DefaultMutableTreeNode(new Result("Result X1"));
        root.add(child_1);
        root.add(child_2);
        child_1.add(child_11);
         // Update the GUI  
         _treePanel.updateTree(root);
         wait(UPDATE_INTERVAL*1000);
     }
}
}
 

TreePanel
_____________________________

  
public class TreePanel extends JPanel {
private JScrollPanel _treeSrcoll;
private JTree _tree;
TreePanel() {
    super();
    // Test tree, displayed in applet�s init() 
    DefaultMutableTreeNode root = new DefaultMutableTreeNode (new Result("Root"));
    DefaultMutableTreeNode child_1 = new DefaultMutableTreeNode (new Result("Result 1"));
    DefaultMutableTreeNode child_2 = new DefaultMutableTreeNode (new Result("Result 2"));
    DefaultMutableTreeNode child_11 = new DefaultMutableTreeNode (new Result("Result 4"));
    DefaultMutableTreeNode child_12 = new DefaultMutableTreeNode (new Result("Result 5"));    
    root.add(child_1);
    root.add(child_2);
    child_1.add(child_11);
    child_1.add(child_12);
    _tree = new JTree(root);
    _treeScroll = new JScrollPane(_tree);
    add(_treeScroll, BorderLayout.CENTER);
}
public void updateTree(DefaultMutableTreeNode  theRoot) {
    if (theRoot != null) {
      if (_tree!= null) {
        _treeScroll.remove(_tree);
      }
      _ tree = new QCTree(root);      
      _treeScroll.add(_tree);
  } else {
     JLabel label = new JLabel("No result tree structure is available");
    _treeScroll.add(label);
  }
   _treeScroll.repaint();
}
}
 

Result
___________________________________

  
public class Result {
  private String _name;  
  public Result(String name) {
    _name = name;
  }
  public String toString() {
      return _name;
   }
}

[Marte J.]

found the error:
I need to use
_treeScroll.getViewPort().add(_tree);
and
_treeScroll.getViewPort().remove(_tree);

[Angela Poynton]

Moving to Applets