invokeAndWait()/invokeLater() ??

[Gregg Bolinger]

In my application I have a JTree that I am going to update every xxx minutes. So I made this class:

public class Anykey_TicketTreeUpdater implements Runnable
{
   public void run()
   {
while(true)
{
     try{        //This is where I will update the tree
                System.out.println ("Hello");
Thread.sleep(5000);
     }catch(InterruptedException e)
     {
     }
}
   }
}

Now I have a class that extends JPanel and in that class I build my tree. After I build my tree I then want to go ahead and start the Runnable class so that the tree will update every xxx minutes.
So I do this:

SwingUtilities.invokeLater(new Anykey_TicketTreeUpdater());

I have also tried

SwingUtilities.invokeAndWait(new Anykey_TicketTreeUpdater());

The problem is that this Runnable starts running, but I never get returned to the GUI. Everything in the GUI just hangs while the Thread runs.
Any ideas?

BTW - This is a JApplet in case that makes a difference.

[Shyam Purkayastha]

You shold not use invokelater().Since invokelater() executes the thread in the event dispatched thread and as your thread runs in an infinite loop it will never end and your application will hang.
Why dont you run it as a seperate thread alltogether.
new Thread(Runable/*your Runnable class*/).start();

[Gregg Bolinger]

Thanks, that seems to work good.

[Chantal Ackermann]

it is right to do the updating in the AWT-main-thread. so I'd suppose it's safer to do this:

final Runnable updateRunnable = new Runnable()
{
updateTree();
}
final Thread pollingThread = new Thread()
{
public void run()
{
try
{
while (!isInterrupted())
{
if (SwingUtilties.isEventDispatchThread())
{
updateRunnable.run();
}
else
{
// invokeAndWait will return only after the update
// while invokeLater returns at once, probably before
// the tree was updated
SwingUtilities.invokeAndWait(updateRunnable);
}

sleep(5000);
}
}
catch(Exception e)
{
System.out.println("Caught exception: " + e.getMessage());
if (SwingUtilties.isEventDispatchThread())
{
// interrupt the thread, even if it was an InterruptedException
Thread.currentThread().interrupt();
}
}
}
}

when you catch the interrupted exception you should call "Thread.currentThread().interrupt()" - unless the current thread is the AWT-main-thread, of course. otherwise the thread does not die.
this polling thread will most probably never be interrupted, but for data retrieval in a gui, it is important.
see this very good article on stopping threads:
http://www.javaspecialists.co.za/archive/Issue056.html
Chantal
[ November 25, 2002: Message edited by: Chantal Ackermann ]