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.google.android.setupdesign.template; 18 19 import androidx.annotation.NonNull; 20 import androidx.annotation.Nullable; 21 import androidx.recyclerview.widget.RecyclerView; 22 import android.util.Log; 23 import com.google.android.setupdesign.template.RequireScrollMixin.ScrollHandlingDelegate; 24 25 /** 26 * {@link ScrollHandlingDelegate} which analyzes scroll events from {@link RecyclerView} and 27 * notifies {@link RequireScrollMixin} about scrollability changes. 28 */ 29 public class RecyclerViewScrollHandlingDelegate implements ScrollHandlingDelegate { 30 31 private static final String TAG = "RVRequireScrollMixin"; 32 33 @Nullable private final RecyclerView recyclerView; 34 35 @NonNull private final RequireScrollMixin requireScrollMixin; 36 RecyclerViewScrollHandlingDelegate( @onNull RequireScrollMixin requireScrollMixin, @Nullable RecyclerView recyclerView)37 public RecyclerViewScrollHandlingDelegate( 38 @NonNull RequireScrollMixin requireScrollMixin, @Nullable RecyclerView recyclerView) { 39 this.requireScrollMixin = requireScrollMixin; 40 this.recyclerView = recyclerView; 41 } 42 canScrollDown()43 private boolean canScrollDown() { 44 if (recyclerView != null) { 45 // Compatibility implementation of View#canScrollVertically 46 final int offset = recyclerView.computeVerticalScrollOffset(); 47 final int range = 48 recyclerView.computeVerticalScrollRange() - recyclerView.computeVerticalScrollExtent(); 49 return range != 0 && offset < range - 1; 50 } 51 return false; 52 } 53 54 @Override startListening()55 public void startListening() { 56 if (this.recyclerView != null) { 57 this.recyclerView.addOnScrollListener( 58 new RecyclerView.OnScrollListener() { 59 @Override 60 public void onScrolled(RecyclerView recyclerView, int dx, int dy) { 61 requireScrollMixin.notifyScrollabilityChange(canScrollDown()); 62 } 63 }); 64 65 if (canScrollDown()) { 66 requireScrollMixin.notifyScrollabilityChange(true); 67 } 68 } else { 69 Log.w(TAG, "Cannot require scroll. Recycler view is null."); 70 } 71 } 72 73 @Override pageScrollDown()74 public void pageScrollDown() { 75 if (recyclerView != null) { 76 final int height = recyclerView.getHeight(); 77 recyclerView.smoothScrollBy(0, height); 78 } 79 } 80 } 81