FocusDelegate.java revision 2a32c7e1264b14a20ed900abadea828b804a46ce 
1/*
2 * Copyright 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
17package androidx.recyclerview.selection;
18
19import android.support.annotation.NonNull;
20import android.support.v7.widget.RecyclerView;
21
22import androidx.recyclerview.selection.ItemDetailsLookup.ItemDetails;
23
24/**
25 * Override methods in this class to provide application specific behaviors
26 * related to focusing item.
27 *
28 * @param <K> Selection key type. @see {@link StorageStrategy} for supported types.
29 */
30public abstract class FocusDelegate<K> {
31
32    static <K> FocusDelegate<K> dummy() {
33        return new FocusDelegate<K>() {
34            @Override
35            public void focusItem(@NonNull ItemDetails<K> item) {
36            }
37
38            @Override
39            public boolean hasFocusedItem() {
40                return false;
41            }
42
43            @Override
44            public int getFocusedPosition() {
45                return RecyclerView.NO_POSITION;
46            }
47
48            @Override
49            public void clearFocus() {
50            }
51        };
52    }
53
54    /**
55     * If environment supports focus, focus {@code item}.
56     */
57    public abstract void focusItem(@NonNull ItemDetails<K> item);
58
59    /**
60     * @return true if there is a focused item.
61     */
62    public abstract boolean hasFocusedItem();
63
64    /**
65     * @return the position of the currently focused item, if any.
66     */
67    public abstract int getFocusedPosition();
68
69    /**
70     * If the environment supports focus and something is focused, unfocus it.
71     */
72    public abstract void clearFocus();
73}
74