Modifying platform/frameworks/base package

I'm planning to开发者_如何学C modify some bits in the platform/frameworks/base project in Android Donut r2. The modifications are very small and goes into java packages android.graphics and android.text (the API isn't affected).

What jar libraries do I have to copy from the recompiled platform? the modifications are small and I don't want to replace the whole system.. I'm trying to replace specific jar libraries.

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Not sure how many 'bits' need modifying, but perhaps you could just try to extend the classes you need?