1 /* 2 * Copyright (C) 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 17 package com.android.documentsui.prefs; 18 19 import android.app.backup.BackupManager; 20 import android.content.SharedPreferences; 21 import android.content.SharedPreferences.OnSharedPreferenceChangeListener; 22 23 import com.android.documentsui.base.ApplicationScope; 24 25 import java.util.function.Consumer; 26 27 /** 28 * A class that monitors changes to the default shared preferences file. If a preference which 29 * should be backed up changed, schedule a backup. 30 * 31 * Also, notifies a callback when such changes are noticed. This is the key mechanism by which 32 * we learn about preference changes in other instances of the app. 33 */ 34 public final class PreferencesMonitor { 35 36 private final String mPackageName; 37 private final SharedPreferences mPrefs; 38 private final OnSharedPreferenceChangeListener mListener = this::onSharedPreferenceChanged; 39 private final Consumer<String> mChangeCallback; 40 PreferencesMonitor( @pplicationScope String packageName, SharedPreferences prefs, Consumer<String> listener)41 public PreferencesMonitor( 42 @ApplicationScope String packageName, 43 SharedPreferences prefs, 44 Consumer<String> listener) { 45 46 mPackageName = packageName; 47 mPrefs = prefs; 48 mChangeCallback = listener; 49 } 50 start()51 public void start() { 52 mPrefs.registerOnSharedPreferenceChangeListener(mListener); 53 } 54 stop()55 public void stop() { 56 mPrefs.unregisterOnSharedPreferenceChangeListener(mListener); 57 } 58 59 // visible for use as a lambda, otherwise treat as a private. onSharedPreferenceChanged(SharedPreferences prefs, String key)60 void onSharedPreferenceChanged(SharedPreferences prefs, String key) { 61 if (Preferences.shouldBackup(key)) { 62 mChangeCallback.accept(key); 63 BackupManager.dataChanged(mPackageName); 64 } 65 } 66 } 67