1 /*
2  * Copyright (C) 2020 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 android.content.res.loader;
18 
19 import android.annotation.NonNull;
20 import android.annotation.Nullable;
21 import android.content.res.AssetFileDescriptor;
22 import android.content.res.AssetManager;
23 import android.os.ParcelFileDescriptor;
24 
25 /**
26  * Provides callbacks that allow for the value of a file-based resources or assets of a
27  * {@link ResourcesProvider} to be specified or overridden.
28  */
29 public interface AssetsProvider {
30 
31     /**
32      * Callback that allows the value of a file-based resources or asset to be specified or
33      * overridden.
34      *
35      * <p>The system will take ownership of the file descriptor returned from this method, so
36      * {@link ParcelFileDescriptor#dup() dup} the file descriptor before returning if the system
37      * should not own it.
38      *
39      * <p>There are two situations in which this method will be called:
40      * <ul>
41      * <li>AssetManager is queried for an InputStream of an asset using APIs like
42      * {@link AssetManager#open} and {@link AssetManager#openXmlResourceParser}.
43      * <li>AssetManager is resolving the value of a file-based resource provided by the
44      * {@link ResourcesProvider} this instance is associated with.
45      * </ul>
46      *
47      * <p>If the value retrieved from this callback is null, AssetManager will attempt to find the
48      * file-based resource or asset within the APK provided by the ResourcesProvider this instance
49      * is associated with.
50      *
51      * @param path the asset path being loaded
52      * @param accessMode the {@link AssetManager} access mode
53      *
54      * @see AssetManager#open
55      */
56     @Nullable
loadAssetFd(@onNull String path, int accessMode)57     default AssetFileDescriptor loadAssetFd(@NonNull String path, int accessMode) {
58         return null;
59     }
60 }
61