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 androidx.core.util.Preconditions.checkArgument;
20
21import androidx.annotation.IntDef;
22import androidx.annotation.NonNull;
23import androidx.annotation.Nullable;
24import androidx.recyclerview.widget.RecyclerView;
25
26import java.lang.annotation.Retention;
27import java.lang.annotation.RetentionPolicy;
28
29/**
30 * Provides selection library access to stable selection keys identifying items
31 * presented by a {@link RecyclerView RecyclerView} instance.
32 *
33 * @param <K> Selection key type. @see {@link StorageStrategy} for supported types.
34 */
35public abstract class ItemKeyProvider<K> {
36
37    /**
38     * Provides access to all data, regardless of whether it is bound to a view or not.
39     * Key providers with this access type enjoy support for enhanced features like:
40     * SHIFT+click range selection, and band selection.
41     */
42    public static final int SCOPE_MAPPED = 0;
43
44    /**
45     * Provides access to cached data based for items that were recently bound in the view.
46     * Employing this provider will result in a reduced feature-set, as some
47     * features like SHIFT+click range selection and band selection are dependent
48     * on mapped access.
49     */
50    public static final int SCOPE_CACHED = 1;
51
52    @IntDef({
53            SCOPE_MAPPED,
54            SCOPE_CACHED
55    })
56    @Retention(RetentionPolicy.SOURCE)
57    public @interface Scope {}
58
59    private final @Scope int mScope;
60
61    /**
62     * Creates a new provider with the given scope.
63     *
64     * @param scope Scope can't be changed at runtime.
65     */
66    protected ItemKeyProvider(@Scope int scope) {
67        checkArgument(scope == SCOPE_MAPPED || scope == SCOPE_CACHED);
68
69        mScope = scope;
70    }
71
72    final boolean hasAccess(@Scope int scope) {
73        return scope == mScope;
74    }
75
76    /**
77     * @return The selection key at the given adapter position, or null.
78     */
79    public abstract @Nullable K getKey(int position);
80
81    /**
82     * @return the position corresponding to the selection key, or RecyclerView.NO_POSITION.
83     */
84    public abstract int getPosition(@NonNull K key);
85}
86