FirebaseIndexRecyclerAdapter<Post, FeedFragment.PostViewHolder> firebaseIndexRecyclerAdapter = new FirebaseIndexRecyclerAdapter<Post, FeedFragment.PostViewHolder>(
Pagination is not supported by FirebaseUI-Android components. They currently require you to provide a single query that yields all the results to display. There is no way to progressively supply more queries as a list is scrolled. Also see the discussion in this issue on the Github repo for FirebaseUI-Android.