Message passing between subcomponents.

[hottimbo]

Hi,

I've got a JApplet class with a JPanel object as the content pane. The content pane Panel has a BorderLayout, with one one JPanel derived class in NORTH, and one JPanel derived class in CENTER.

The center panel is a map on which places can be selected. I want the NORTH panel to display info on the place selected, but can't figure out a way for the center panel to notify the north panel that something has changed in the state of the center panel, and to pass the data and update the screen.

Do I need to create a thread in the north panel which constantly monitors the state of the center panel ?

Thanks,
Tim

 

[sedj]

If you add use the

JPanel

addMouseListener

and or

addMouseMotionListener

methods inherited from

java.awt.Component

, you can listen for mouse movements and clicks - which when the user clicks on the specific panel - you can catch the event, and do stuff with it (ie update the other panel).

Check out the documentation :

http://java.sun.com/j2se/1.3/docs/api/javax/swing/JPanel.html

Ben

 

[hottimbo]

Thanks, that makes sense. I'll do that.

I currently have a mouse listener in the center panel doing this, so I can't seem to trap those mouse messages in the main JApplet.
I guess I'll handle all the mouse stuff in the main applet like you suggest, and not in the individual components.

I've also moved the animation thread from the center panel to the main applet, which has raised a new problem.

I'm calling the JApplet's overridden paint() every 50ms or so. Inside that paint() I do some data handling then call super.paint(), which (should) then go and paint the other sub components. This works, except that occasionally (once every couple of seconds) it renders the center panel from the north position and causes it to appear to jump every so often.

Am I doing this wrong too ?

Thanks,
Tim