How to change scene graph from listener thread?

Question

Greetings,
I need a little help with javafx.concurrency.Task - I think.
I have a JavaFX program that is listening for JMX Notifications. When I receive certain notifications, I want to change the scene graph. Of course, the notifications are being received on a thread kicked off by RMI, not the JavaFX Application thread -- so anything I try to do to the scene graph there won't work.
I've look at Richard Bair's article: http://fxexperience.com/2011/07/worker-threading-in-javafx-2-0/
and other examples, but every example I've found involves kicking off the Task from the Application thread and observing some property of the Task.
I think I somehow need by Notification listener to queue up the things that need to be done to the scene graph somewhere, and then have a thread started from the Application thread read the queue and actually make the changes.
I could use a pointer to an example, or even a general overview of how this type of thing should be accomplished. I could post a code example if needed, but it will take some doing and it wouldn't even be working.
Thanks,
Cameron

Answer 1

Tasks/Service are most useful when you are initiating the action via the GUI (i.e. as a result of a button press, a mouse event, a keyboard action, etc). In your case JMX/RMI will be running an internal 'listener' thread which is triggering your handler method. In this case the best option is to just use Platform.runLater.
Something like the following"
{code}
public void handleEventFromServer(final MyData dataFromServer)
Platform.runLater(new Runnable() {
public void run()
// this will be done in your GUI thread so you can update the GUI here
myTextField.setText("Result from server is: " + dataFromServer.getSomeValue());
{code}
If you have some sort of JmxListener interface you could just create a ThreadSafe event propagator like so:
{code}
public class ThreadSafeJmxListener implements JmxListener
private JmxListener actualListener;
public ThreadSafeJmxListener(JmxListener actualListener)
this.actualListener = actualListener;
@Override
public void handleJmxEvent(final JmxEvent event)
Platform.runLater(new Runnable() {
public void run()
actualListener.handleJmxEvent(event);
{code}
Then just use it something like so:
{code}
jmxChannel.addJmxListener(new ThreadSafeJmxListener(new JmxHandler()
public void handleJmxEvent(final JmxEvent event)
// this will be done in your GUI thread so you can update the GUI here
myTextField.setText("Result from server is: " + dataFromServer.getSomeValue());
{code}
If you want to send data to the server, use a task (or service) for that. If you need more info on that, post back, but there is a fair bit of that in this forum, or on various blogs (you'll find a fair few examples buried in my posts: http://zenjava.com).