How to gain control of trackball in Nexus One Android

I'm kind of new in android AOSP development, and I'm trying to click to the trackball and launch an app already installed (Camera App).

I'm looking at the policy.androdoid, but i just doesn't understand how to gain controls of the hardware buttons and where to s开发者_开发知识库tart.

Any help, source code example or something like that will be really helpful.

Thanks in advance!

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Not sure I completely understand your question but try looking here http://developer.android.com/guide/topics/ui/ui-events.html

As for the starting camera using Intent look at the example here