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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.systemui.accessibility;
import android.content.ContentResolver;
import android.content.Context;
import android.database.ContentObserver;
import android.os.Handler;
import android.os.Looper;
import android.os.UserHandle;
import android.provider.Settings;
import androidx.annotation.NonNull;
import com.android.internal.annotations.VisibleForTesting;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
/**
* Provides basic methods for adding, removing arbitrary listeners and inquiry given {@code
* secureSettingsKey} value; it must comes from {@link Settings.Secure}.
*
* This abstract class is intended to be subclassed and specialized to maintain
* a registry of listeners of specific types and dispatch changes to them.
*
* @param <T> The listener type
*/
public abstract class SecureSettingsContentObserver<T> {
private final ContentResolver mContentResolver;
@VisibleForTesting
final ContentObserver mContentObserver;
private final String mKey;
@VisibleForTesting
final List<T> mListeners = new ArrayList<>();
protected SecureSettingsContentObserver(Context context, String secureSettingsKey) {
mKey = secureSettingsKey;
mContentResolver = context.getContentResolver();
mContentObserver = new ContentObserver(new Handler(Looper.getMainLooper())) {
@Override
public void onChange(boolean selfChange) {
updateValueChanged();
}
};
}
/**
* Registers a listener to receive updates from given settings key {@code secureSettingsKey}.
*
* @param listener A listener to be added to receive the changes
*/
public void addListener(@NonNull T listener) {
Objects.requireNonNull(listener, "listener must be non-null");
if (!mListeners.contains(listener)) {
mListeners.add(listener);
}
if (mListeners.size() == 1) {
mContentResolver.registerContentObserver(
Settings.Secure.getUriFor(mKey), /* notifyForDescendants= */
false, mContentObserver, UserHandle.USER_ALL);
}
}
/**
* Unregisters a listener previously registered with {@link #addListener(T listener)}.
*
* @param listener A listener to be removed from receiving the changes
*/
public void removeListener(@NonNull T listener) {
Objects.requireNonNull(listener, "listener must be non-null");
mListeners.remove(listener);
if (mListeners.isEmpty()) {
mContentResolver.unregisterContentObserver(mContentObserver);
}
}
/**
* Gets the value from the current user's secure settings.
*
* See {@link Settings.Secure}.
*/
public final String getSettingsValue() {
return Settings.Secure.getStringForUser(mContentResolver, mKey, UserHandle.USER_CURRENT);
}
private void updateValueChanged() {
final String value = getSettingsValue();
final int listenerSize = mListeners.size();
for (int i = 0; i < listenerSize; i++) {
onValueChanged(mListeners.get(i), value);
}
}
/**
* Called when the registered value from {@code secureSettingsKey} changes.
*
* @param listener A listener could be used to receive the updates
* @param value Content changed value from {@code secureSettingsKey}
*/
abstract void onValueChanged(T listener, String value);
}
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