Programmatically change GUI controls/ prevent event firing

Question

Hi,
I often construct GUIs where user input in one control automatically changes other controls.
A (simple) example:
A GUI contains controls A and B. When the user changes control A the value of control B has to be adjusted, and the other way round. So the event handler of A tells B to change its value. An event is fired, and the event handler of B tells A to change its value. An event is fired... and you have an endless event handling loop.
Please believe me, though the example is simple: this happens frequently in real life, too. Since setting Swing controls programmatically most often triggers events, I need a mechanism to prevent event handling loops. What I do so far is
o set a "deaf" flag
o change the control
o the listener gets informed about the change, but since the "deaf" flag is set it does nothing
o reset the "deaf" flag
Another, equally awkward way, is removing event listeners before the change and reattaching them afterwards.
Is there any elegant way to handle this? How do you handle this kind of problem, which can't be too rare in the GUI world (although a rather extensive search with Google did not find much)?
Chris

Answer 1

Personally, I usually choose the same approach as you did, implementing a flag which I'll check when events are fired. If you do this, however, be sure to make the flag volatile, otherwise it might (very rarely) happen that a thread caches the value (even though this points to faulty code on your side, it is well near impossible to debug). I would strongly recomment not to remove and readd the listeners since it will create a lot of overhead and is rather hard to maintain.