1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.setupwizardlib.template; 18 19 import android.support.annotation.NonNull; 20 import android.support.annotation.Nullable; 21 import android.support.v7.widget.RecyclerView; 22 import android.util.Log; 23 24 import com.android.setupwizardlib.template.RequireScrollMixin.ScrollHandlingDelegate; 25 26 /** 27 * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link RecyclerView} and 28 * notifies {@link RequireScrollMixin} about scrollability changes. 29 */ 30 public class RecyclerViewScrollHandlingDelegate implements ScrollHandlingDelegate { 31 32 private static final String TAG = "RVRequireScrollMixin"; 33 34 @Nullable 35 private final RecyclerView mRecyclerView; 36 37 @NonNull 38 private final RequireScrollMixin mRequireScrollMixin; 39 40 public RecyclerViewScrollHandlingDelegate( 41 @NonNull RequireScrollMixin requireScrollMixin, 42 @Nullable RecyclerView recyclerView) { 43 mRequireScrollMixin = requireScrollMixin; 44 mRecyclerView = recyclerView; 45 } 46 47 private boolean canScrollDown() { 48 if (mRecyclerView != null) { 49 // Compatibility implementation of View#canScrollVertically 50 final int offset = mRecyclerView.computeVerticalScrollOffset(); 51 final int range = mRecyclerView.computeVerticalScrollRange() 52 - mRecyclerView.computeVerticalScrollExtent(); 53 return range != 0 && offset < range - 1; 54 } 55 return false; 56 } 57 58 @Override 59 public void startListening() { 60 if (mRecyclerView != null) { 61 mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { 62 @Override 63 public void onScrolled(RecyclerView recyclerView, int dx, int dy) { 64 mRequireScrollMixin.notifyScrollabilityChange(canScrollDown()); 65 } 66 }); 67 68 if (canScrollDown()) { 69 mRequireScrollMixin.notifyScrollabilityChange(true); 70 } 71 } else { 72 Log.w(TAG, "Cannot require scroll. Recycler view is null."); 73 } 74 } 75 76 @Override 77 public void pageScrollDown() { 78 if (mRecyclerView != null) { 79 final int height = mRecyclerView.getHeight(); 80 mRecyclerView.smoothScrollBy(0, height); 81 } 82 } 83 } 84
