| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package com.example.android.wearable.wear.messaging.util; |
| |
| import android.support.v7.widget.RecyclerView; |
| import android.util.Log; |
| import android.view.ViewTreeObserver; |
| |
| /** Prescrolls to the last element in the adapter before draw and removes itself. */ |
| public class PrescrollToBottom implements ViewTreeObserver.OnPreDrawListener { |
| |
| private static final String TAG = "PrescrollToBottom"; |
| |
| private RecyclerView mRecyclerView; |
| private RecyclerView.Adapter mAdapter; |
| |
| public PrescrollToBottom(RecyclerView recyclerView, RecyclerView.Adapter adapter) { |
| mRecyclerView = recyclerView; |
| mAdapter = adapter; |
| } |
| |
| @Override |
| public boolean onPreDraw() { |
| boolean shouldScroll = mAdapter.getItemCount() > 2; |
| if (shouldScroll) { |
| Log.d(TAG, "Smooth scrolling after draw to position " + mAdapter.getItemCount()); |
| mRecyclerView.smoothScrollToPosition(mAdapter.getItemCount()); |
| } |
| // always remove the listener so that we do not get multiple |
| // instances of it attached when it is not needed |
| mRecyclerView.getViewTreeObserver().removeOnPreDrawListener(this); |
| return !shouldScroll; |
| } |
| } |