findFragmentById always returns null

Question

I\'m defining an ID for my fragment in the xml layout:

Answer 1

I was using android.support.v4.app.Fragment in my layout while calling getFragmentManager() which actually searched for android.app.Fragment subclasses and I got null. So the fix was to call getSupportFragmentManager() instead.

In general make sure the package of a fragment you are subclassing and using in your layout is the same returned by the corresponding FragmentManager which performs search.