1 /*
2  * Copyright 2018 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 package androidx.recyclerview.widget;
17 
18 import org.jspecify.annotations.Nullable;
19 
20 /**
21  * An interface that can receive Update operations that are applied to a list.
22  * <p>
23  * This class can be used together with DiffUtil to detect changes between two lists.
24  */
25 public interface ListUpdateCallback {
26     /**
27      * Called when {@code count} number of items are inserted at the given position.
28      *
29      * @param position The position of the new item.
30      * @param count    The number of items that have been added.
31      */
onInserted(int position, int count)32     void onInserted(int position, int count);
33 
34     /**
35      * Called when {@code count} number of items are removed from the given position.
36      *
37      * @param position The position of the item which has been removed.
38      * @param count    The number of items which have been removed.
39      */
onRemoved(int position, int count)40     void onRemoved(int position, int count);
41 
42     /**
43      * Called when an item changes its position in the list.
44      *
45      * @param fromPosition The previous position of the item before the move.
46      * @param toPosition   The new position of the item.
47      */
onMoved(int fromPosition, int toPosition)48     void onMoved(int fromPosition, int toPosition);
49 
50     /**
51      * Called when {@code count} number of items are updated at the given position.
52      *
53      * @param position The position of the item which has been updated.
54      * @param count    The number of items which has changed.
55      * @param payload  The payload for the changed items.
56      */
onChanged(int position, int count, @Nullable Object payload)57     void onChanged(int position, int count, @Nullable Object payload);
58 }
59