Force closed if my custom ViewGroup called onLayout directly

[hendrawd]

I have a custom ViewGroup that called onLayout directly, but this line scrollListener.updateHandlePosition(recyclerView); will make application force closed with error java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v7.widget.RecyclerView.computeVerticalScrollOffset()' on a null object reference

Actually i could avoid the force closed easily by setting mFastScroller.setRecyclerView(mRecyclerView); twice: after findViewById and after mRecyclerView.setAdapter(mAdapter);

But i think it will be more useful if the library itself check for null object directly before set any value to it.