Android comes with lots of system resources (
You can find a full listing of all system resources in the android package.
Every time I want to do something on Android I check to see if there's a system resource that covers what I want to do. It is helpful to import the Android source code (in particular, their /res/ folder) when searching for already-implemented resources that you might want, so you can see their specific implementation.
Personally, I find myself most often using:
android.R.id), because you are often required to use these if you want to use some of Android's widgets (for example,
TabHost/TabWidgetrequires you to use "
android:id/tabs" and "
android:id/tabcontent" if you want to implement an XML layout).