FirebaseUI-Android: FirebaseRecyclerAdapter and RecyclerView scroll position is lost on orientation change

Environment

• Android device: API 27 Emulator / Google Pixel
• Android OS version: 27 / 8.0.0
• Google Play Services version: whatever the emulator has / 11.7.45 (940-174122868)
• Firebase/Play Services SDK version: 11.4.2
• FirebaseUI version: 3.1.0

The problem:

On orientation change the recycler view using FirebaseRecyclerAdapter looses it’s scroll position and is always scrolled to the top.

Steps to reproduce:

1. In the https://github.com/firebase/FirebaseUI-Android/blob/master/app/src/main/java/com/firebase/uidemo/database/realtime/RealtimeDbChatActivity.java#L110 comment out:

        // Scroll to bottom on new messages
        adapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
            @Override
            public void onItemRangeInserted(int positionStart, int itemCount) {
                mRecyclerView.smoothScrollToPosition(adapter.getItemCount());
            }
        });

so it does not get execute. This is needed so there is no extra logic forcing a scroll position. 2. Build the demo app 3. Add a bunch of chat messages, a lot so you get a scrolling regardless of orientation 4. Scroll neither to the top nor the bottom 5. Rotate the emulator

Observed Results:

• After rotation the recycler view lost it’s scroll position and is scrolled to the top.

Expected Results:

• The recycler view should keep it’s scroll position on orientation change.