Java.Observable

Donald-Duck

I have a JFrame observing another class. And this works fine when I launch the JFrame normally. However when I create the JFrame from within another JFrame, the Observing JFrame does not observe. It just stays with its default values for everything.

I'm adding the observer using object.addObserver(this);

marco_polo

It is probably not working because JFrame is a Top Level component and it does not make sense to create one inside another, and will probably result in all kinds of unexpected behaviour. If you want a window within a window in your application use a JDialog or an Internal Frame instead.

See here for more details

http://java.sun.com/docs/books/tutorial/uiswing/components/toplevel.html

Donald-Duck

Sorry I meant opening a new JFrame, in a new window, from a button in original one.

marco_polo

Could you post up a little more code perhaps? Don't have much to go on at the moment. Where is object.addObserver(this); called from for example?

Donald-Duck

public class GameWindow extends JFrame implements java.util.Observer
{
	public GameWindow() {
        	...
            	aTable.addObserver(this);
            	aTable.initialise();           
	}
}

public class Table extends java.util.Observable {
	
	public Table() {
		...
	}
	...
}

class LoginWindow {
	private void singlePlayerClicked()
	{
			GameWindow g = new GameWindow();
	}
}

If the code is left to wait for user interaction in the GameWindow JFrame it just freezes as a white window, with the observed Table running correctly.
If I remove the user interaction, the GameWindow runs fine, JFrame opens correctly however it doesn't observe the Table correctly and none of the values are ever updated in the JFrame.

I think I've included what I think are the important parts of the code, I didn't originally write most of it as it was done by another guy in the project group.

clearz

In your aTable.initialise(); method try adding

setChanged();
notifyObservers();

at the end. Not sure if this is where you want the callback to happen but.

Donald-Duck

Unfortuantely thats in it already.

If I was to launch GameWindow from main it all works perfectly.

clearz

Donald-Duck wrote: »

Unfortuantely thats in it already.

If I was to launch GameWindow from main it all works perfectly.

Well then as marco_polo has said can you show us all code releated to the observer pattern

Donald-Duck

I'll get the guy who wrote it to write a smaller project that causes the same bug, couple of thousand lines involved so it'd be pretty tedious for anyone here to look through.

marco_polo

I got the brain going and I think I have an answer. I suspect that it is a threading issue.

The JVM uses a single thread per JVM to handle all GUI events called the event dispatch thread. As you are creating the second JFrame within this event handling thread (when the user clicks a button) it is likely the cause of your problem.

If you kick off a new thread for the second JFrame I think it should work ok.

Something like this should do

private void singlePlayerClicked(){

    Runnable r = new Runnable() {
          public void run() {
              new GameWindow();
          }
    });
Thread.start (r)


	

** EDIT oh wait when you remove the user interaction it still doesn't observe.
Only half way there so