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 androidx.leanback.widget; 18 19 import androidx.annotation.NonNull; 20 import androidx.recyclerview.widget.DiffUtil; 21 22 import java.util.List; 23 24 /** 25 * Callback that informs {@link ArrayObjectAdapter} how to compute list updates when using 26 * {@link DiffUtil} in {@link ArrayObjectAdapter#setItems(List, 27 * DiffCallback)} method. 28 * <p> 29 * The {@link ArrayObjectAdapter#setItems(List, 30 * DiffCallback)} method will pass items from different 31 * lists to this callback in order to implement 32 * the {@link DiffUtil.Callback} it uses to compute differences between 33 * lists. 34 * 35 * @paramType of items to compare. 36 */ 37 public abstract class DiffCallback<Value> { 38 /** 39 * Called to decide whether two objects represent the same item. 40 * 41 * @param oldItem The item in the old list. 42 * @param newItem The item in the new list. 43 * @return True if the two items represent the same object or false if they are different. 44 * @see DiffUtil.Callback#areItemsTheSame(int, int) 45 */ 46 public abstract boolean areItemsTheSame(@NonNull Value oldItem, @NonNull Value newItem); 47 48 /** 49 * Called to decide whether two items have the same data. This information is used to detect if 50 * the contents of an item have changed. 51 * 52 * @param oldItem The item in the old list. 53 * @param newItem The item in the new list. 54 * @return True if the contents of the items are the same or false if they are different. 55 * @see DiffUtil.Callback#areContentsTheSame(int, int) 56 */ 57 public abstract boolean areContentsTheSame(@NonNull Value oldItem, @NonNull Value newItem); 58 59 /** 60 * Called to get a change payload between an old and new version of an item. 61 * 62 * @see DiffUtil.Callback#getChangePayload(int, int) 63 */ 64 @SuppressWarnings("WeakerAccess") 65 public Object getChangePayload(@NonNull Value oldItem, @NonNull Value newItem) { 66 return null; 67 } 68 } 69
