1 /*
2  * Copyright (C) 2021 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 com.android.systemui.accessibility;
18 
19 import android.content.ContentResolver;
20 import android.content.Context;
21 import android.database.ContentObserver;
22 import android.os.Handler;
23 import android.os.Looper;
24 import android.os.UserHandle;
25 import android.provider.Settings;
26 
27 import androidx.annotation.NonNull;
28 
29 import com.android.internal.annotations.VisibleForTesting;
30 
31 import java.util.ArrayList;
32 import java.util.List;
33 import java.util.Objects;
34 
35 /**
36  * Provides basic methods for adding, removing arbitrary listeners and inquiry given {@code
37  * secureSettingsKey} value; it must comes from {@link Settings.Secure}.
38  *
39  * This abstract class is intended to be subclassed and specialized to maintain
40  * a registry of listeners of specific types and dispatch changes to them.
41  *
42  * @param <T> The listener type
43  */
44 public abstract class SecureSettingsContentObserver<T> {
45 
46     private final ContentResolver mContentResolver;
47     @VisibleForTesting
48     final ContentObserver mContentObserver;
49 
50     private final String mKey;
51 
52     @VisibleForTesting
53     final List<T> mListeners = new ArrayList<>();
54 
SecureSettingsContentObserver(Context context, String secureSettingsKey)55     protected SecureSettingsContentObserver(Context context, String secureSettingsKey) {
56         mKey = secureSettingsKey;
57         mContentResolver = context.getContentResolver();
58         mContentObserver = new ContentObserver(new Handler(Looper.getMainLooper())) {
59             @Override
60             public void onChange(boolean selfChange) {
61                 updateValueChanged();
62             }
63         };
64     }
65 
66     /**
67      * Registers a listener to receive updates from given settings key {@code secureSettingsKey}.
68      *
69      * @param listener A listener to be added to receive the changes
70      */
addListener(@onNull T listener)71     public void addListener(@NonNull T listener) {
72         Objects.requireNonNull(listener, "listener must be non-null");
73 
74         if (!mListeners.contains(listener)) {
75             mListeners.add(listener);
76         }
77 
78         if (mListeners.size() == 1) {
79             mContentResolver.registerContentObserver(
80                     Settings.Secure.getUriFor(mKey), /* notifyForDescendants= */
81                     false, mContentObserver, UserHandle.USER_ALL);
82         }
83     }
84 
85     /**
86      * Unregisters a listener previously registered with {@link #addListener(T listener)}.
87      *
88      * @param listener A listener to be removed from receiving the changes
89      */
removeListener(@onNull T listener)90     public void removeListener(@NonNull T listener) {
91         Objects.requireNonNull(listener, "listener must be non-null");
92 
93         mListeners.remove(listener);
94 
95         if (mListeners.isEmpty()) {
96             mContentResolver.unregisterContentObserver(mContentObserver);
97         }
98     }
99 
100     /**
101      * Gets the value from the current user's secure settings.
102      *
103      * See {@link Settings.Secure}.
104      */
getSettingsValue()105     public final String getSettingsValue() {
106         return Settings.Secure.getStringForUser(mContentResolver, mKey, UserHandle.USER_CURRENT);
107     }
108 
updateValueChanged()109     private void updateValueChanged() {
110         final String value = getSettingsValue();
111         final int listenerSize = mListeners.size();
112         for (int i = 0; i < listenerSize; i++) {
113             onValueChanged(mListeners.get(i), value);
114         }
115     }
116 
117     /**
118      * Called when the registered value from {@code secureSettingsKey} changes.
119      *
120      * @param listener A listener could be used to receive the updates
121      * @param value Content changed value from {@code secureSettingsKey}
122      */
onValueChanged(T listener, String value)123     abstract void onValueChanged(T listener, String value);
124 }
125