1 /* 2 * Copyright (C) 2013 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.server; 18 19 import android.os.Handler; 20 import android.os.Trace; 21 22 /** 23 * Shared singleton foreground thread for the system. This is a thread for 24 * operations that affect what's on the display, which needs to have a minimum 25 * of latency. This thread should pretty much only be used by the WindowManager, 26 * DisplayManager, and InputManager to perform quick operations in real time. 27 */ 28 public final class DisplayThread extends ServiceThread { 29 private static DisplayThread sInstance; 30 private static Handler sHandler; 31 32 private DisplayThread() { 33 super("android.display", android.os.Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/); 34 } 35 36 private static void ensureThreadLocked() { 37 if (sInstance == null) { 38 sInstance = new DisplayThread(); 39 sInstance.start(); 40 sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER); 41 sHandler = new Handler(sInstance.getLooper()); 42 } 43 } 44 45 public static DisplayThread get() { 46 synchronized (DisplayThread.class) { 47 ensureThreadLocked(); 48 return sInstance; 49 } 50 } 51 52 public static Handler getHandler() { 53 synchronized (DisplayThread.class) { 54 ensureThreadLocked(); 55 return sHandler; 56 } 57 } 58 } 59