content: /**
   * Copyright (C) 2016 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.server.vr;
  
  import android.annotation.NonNull;
  import android.content.BroadcastReceiver;
  import android.content.ContentResolver;
  import android.content.Context;
  import android.content.Intent;
  import android.database.ContentObserver;
  import android.net.Uri;
  import android.os.Handler;
  import android.os.UserHandle;
  import android.provider.Settings;
  import android.util.ArraySet;
  
  import java.util.Objects;
  import java.util.Set;
  
  /**
   * Detects changes in a given setting.
   *
   * @hide
   */
  public class SettingsObserver {
  
      private final String mSecureSettingName;
      private final BroadcastReceiver mSettingRestoreReceiver;
      private final ContentObserver mContentObserver;
      private final Set<SettingChangeListener> mSettingsListeners = new ArraySet<>();
  
      /**
       * Implement this to receive callbacks when the setting tracked by this observer changes.
       */
      public interface SettingChangeListener {
  
          /**
           * Called when the tracked setting has changed.
           */
          void onSettingChanged();
  
  
          /**
           * Called when the tracked setting has been restored for a particular user.
           *
           * @param prevValue the previous value of the setting.
           * @param newValue the new value of the setting.
           * @param userId the user ID for which this setting has been restored.
           */
          void onSettingRestored(String prevValue, String newValue, int userId);
      }
  
      private SettingsObserver(@NonNull final Context context, @NonNull final Handler handler,
              @NonNull final Uri settingUri, @NonNull final String secureSettingName) {
  
          mSecureSettingName = secureSettingName;
          mSettingRestoreReceiver = new BroadcastReceiver() {
              @Override
              public void onReceive(Context context, Intent intent) {
                  if (Intent.ACTION_SETTING_RESTORED.equals(intent.getAction())) {
                      String element = intent.getStringExtra(Intent.EXTRA_SETTING_NAME);
                      if (Objects.equals(element, secureSettingName)) {
                          String prevValue = intent.getStringExtra(Intent.EXTRA_SETTING_PREVIOUS_VALUE);
                          String newValue = intent.getStringExtra(Intent.EXTRA_SETTING_NEW_VALUE);
                          sendSettingRestored(prevValue, newValue, getSendingUserId());
                      }
                  }
              }
          };
  
          mContentObserver = new ContentObserver(handler) {
              @Override
              public void onChange(boolean selfChange, Uri uri) {
                  if (uri == null || settingUri.equals(uri)) {
                      sendSettingChanged();
                  }
              }
          };
  
          ContentResolver resolver = context.getContentResolver();
          resolver.registerContentObserver(settingUri, false, mContentObserver,
                  UserHandle.USER_ALL);
      }
  
      /**
       * Create a SettingsObserver instance.
       *
       * @param context the context to query for settings changes.
       * @param handler the handler to use for a settings ContentObserver.
       * @param settingName the setting to track.
       * @return a SettingsObserver instance.
       */
      public static SettingsObserver build(@NonNull Context context, @NonNull Handler handler,
              @NonNull String settingName) {
          Uri settingUri = Settings.Secure.getUriFor(settingName);
  
          return new SettingsObserver(context, handler, settingUri, settingName);
      }
  
      /**
       * Add a listener for setting changes.
       *
       * @param listener a {@link SettingChangeListener} instance.
       */
      public void addListener(@NonNull SettingChangeListener listener) {
          mSettingsListeners.add(listener);
      }
  
      /**
       * Remove a listener for setting changes.
       *
       * @param listener a {@link SettingChangeListener} instance.
       */
      public void removeListener(@NonNull SettingChangeListener listener) {
          mSettingsListeners.remove(listener);
  
      }
  
      private void sendSettingChanged() {
          for (SettingChangeListener l : mSettingsListeners) {
              l.onSettingChanged();
          }
      }
  
      private void sendSettingRestored(final String prevValue, final String newValue, final int userId) {
          for (SettingChangeListener l : mSettingsListeners) {
              l.onSettingRestored(prevValue, newValue, userId);
          }
      }
  
  }
  