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.permission.util; 18 19 import android.annotation.NonNull; 20 import android.os.Handler; 21 import android.os.HandlerExecutor; 22 import android.os.HandlerThread; 23 24 import com.android.internal.annotations.GuardedBy; 25 26 import java.util.concurrent.Executor; 27 28 /** 29 * Shared singleton background thread. 30 */ 31 public class BackgroundThread extends HandlerThread { 32 private static final Object sLock = new Object(); 33 34 @GuardedBy("sLock") 35 private static BackgroundThread sInstance; 36 @GuardedBy("sLock") 37 private static Handler sHandler; 38 @GuardedBy("sLock") 39 private static Executor sExecutor; 40 BackgroundThread()41 private BackgroundThread() { 42 super(BackgroundThread.class.getName()); 43 } 44 45 @GuardedBy("sLock") ensureInstanceLocked()46 private static void ensureInstanceLocked() { 47 if (sInstance == null) { 48 sInstance = new BackgroundThread(); 49 sInstance.start(); 50 sHandler = new Handler(sInstance.getLooper()); 51 sExecutor = new HandlerExecutor(sHandler); 52 } 53 } 54 55 /** 56 * Get the singleton instance of thi class. 57 * 58 * @return the singleton instance of thi class 59 */ 60 @NonNull get()61 public static BackgroundThread get() { 62 synchronized (sLock) { 63 ensureInstanceLocked(); 64 return sInstance; 65 } 66 } 67 68 /** 69 * Get the {@link Handler} for this thread. 70 * 71 * @return the {@link Handler} for this thread. 72 */ 73 @NonNull getHandler()74 public static Handler getHandler() { 75 synchronized (sLock) { 76 ensureInstanceLocked(); 77 return sHandler; 78 } 79 } 80 81 /** 82 * Get the {@link Executor} for this thread. 83 * 84 * @return the {@link Executor} for this thread. 85 */ 86 @NonNull getExecutor()87 public static Executor getExecutor() { 88 synchronized (sLock) { 89 ensureInstanceLocked(); 90 return sExecutor; 91 } 92 } 93 } 94