[APPLET][Heritage] Problem with classes

Question

Hi, I'm developping a simple JAVA Applet and I have a problem
I have a class called LUIweb which is the main class. Here is a part of it.
public class LUIweb extends JApplet implements Runnable {
public void run() {
DisplayMessage("JAVA rocks");
public void DisplayMessage(String message){
jtextArea.append(message);
middlePanel.removeAll();
middlePanel.add(textScrollPane, BorderLayout.CENTER);
middlePanel.validate();
middlePanel.repaint();
It displays the message "JAVA rocks" in my JTextArea. But when another class from the same package calls DisplayMessage, nothing is displayed in my JTextArea
public class Data_net extends LUIweb{
public void Test(){
DisplayMessage("NON");
Have you got any idea to fix that?
Thank you for you help

Answer 1

OK,
You are using a separate thread to update the gui. As swing is not multithread safe, this is not good. Anytime you want to change the gui, you must do it on the gui thread. This means without extra help, you should only change the gui from within a Listener, such as a MouseListener, KeyListener, etc, etc.
In your case, you are updating the not from the gui thread (not from a Listener), and so you must ask the gui thread to do the work for you when it has time.
This means you need to use SwingUtilities.invokeLater or SwingUtilities.invokeAndWait.
Since the sequencing is important to you in your code, you should probably use invokeAndWait, such as
public void run()
          SwingUtilities.invokeAndWait( new Runnable()
                 public void run() { DisplayMessage(Language.CONNECT_DB); }
          Data_net Donnee_net=new Data_net();          
          SwingUtilities.invokeAndWait( new Runnable()
                 public void run() { DisplayMessage("Connecting to "+Donnee_net.GetHost()+
                                                   " with user "+Donnee_net.GetUser()+"...\n");
          Donnee_net.Test();