FocusDelegate.java revision 63d2846409d84487d4856d3b8d18cc4684352e29 
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 static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;
20
21import android.support.annotation.RestrictTo;
22import android.support.v7.widget.RecyclerView;
23
24import androidx.recyclerview.selection.ItemDetailsLookup.ItemDetails;
25
26/**
27 * Override methods in this class to connect specialized behaviors of the selection
28 * code to the application environment.
29 *
30 * @param <K> Selection key type. Usually String or Long.
31 *
32 * @hide
33 */
34@RestrictTo(LIBRARY_GROUP)
35public abstract class FocusCallbacks<K> {
36
37    static final <K> FocusCallbacks<K> dummy() {
38        return new FocusCallbacks<K>() {
39            @Override
40            public void focusItem(ItemDetails<K> item) {
41            }
42
43            @Override
44            public boolean hasFocusedItem() {
45                return false;
46            }
47
48            @Override
49            public int getFocusedPosition() {
50                return RecyclerView.NO_POSITION;
51            }
52
53            @Override
54            public void clearFocus() {
55            }
56        };
57    }
58
59    /**
60     * If environment supports focus, focus {@code item}.
61     */
62    public abstract void focusItem(ItemDetails<K> item);
63
64    /**
65     * @return true if there is a focused item.
66     */
67    public abstract boolean hasFocusedItem();
68
69    /**
70     * @return the position of the currently focused item, if any.
71     */
72    public abstract int getFocusedPosition();
73
74    /**
75     * If the environment supports focus and something is focused, unfocus it.
76     */
77    public abstract void clearFocus();
78}
79