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Graphics, AWT, Swing I part<br />
Q: Need I to remove all the listeners on all of the components in the Frame when<br />
I close window of the Frame?<br />
I've got a Frame, which has in it a bunch of components, some of which themselves<br />
may be containers. Many of the components in this frame have listeners.<br />
When somebody closes the window of the Frame, I want to completely get rid of the<br />
Frame, so that the garbage collector will later clean it up, freeing it's memory.<br />
However, I haven't yet figured out a way to do this without tracking every single<br />
component by myself. Just calling dispose() on the main Frame doesn't seem to be<br />
good enough. Calling "RemoveAll()", even recursively, doesn't seem to be good<br />
enough.<br />
I *suspect* that the problem may be that I have to remove all the listeners on all of<br />
the components in the Frame. Is there a way to get a list of the listeners out of a<br />
given component? I really don't want to have to track every single button I add to<br />
every single Frame, and every single Listener I add to every single component. If I<br />
have to keep track of all of that, it sort of defeats a lot of the advantages of a<br />
well-defined object oriented system.<br />
Answer: I think you're slightly confused here. When another object registers as a<br />
listener for a component within the frame, it's the component within the frame that is<br />
holding a reference to the external object in its listeners list - not vice versa.<br />
Which means you don't really need to explicitly remove every listener that any other<br />
object registered on components in the frame.<br />
What you need to worry about is however the listeners that the frame itself registered<br />
with some other components that are still alive. If the frame gets disposed without<br />
removing these, the objects that were being listened to will retain a reference to the<br />
frame and this can cause the frame to stay around as long as these objects which<br />
hold these references stay alive.<br />
So look for all Listeners that your frame registered itself as on components external<br />
to itself (should be fairly easy to see since you normally do it in your constructor) and<br />
remove those before disposing off the frame.<br />
--<br />
Kala<br />
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file:///F|/350_t/350_tips/graphics-I.htm (5 of 6) [2002-02-27 21:18:07]
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