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      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.Looper;
     21 import android.os.Process;
     22 import android.os.Trace;
     23 
     24 /**
     25  * Shared singleton thread for showing UI.  This is a foreground thread, and in
     26  * additional should not have operations that can take more than a few ms scheduled
     27  * on it to avoid UI jank.
     28  */
     29 public final class UiThread extends ServiceThread {
     30     private static final long SLOW_DISPATCH_THRESHOLD_MS = 100;
     31     private static UiThread sInstance;
     32     private static Handler sHandler;
     33 
     34     private UiThread() {
     35         super("android.ui", Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
     36     }
     37 
     38     @Override
     39     public void run() {
     40         // Make sure UiThread is in the fg stune boost group
     41         Process.setThreadGroup(Process.myTid(), Process.THREAD_GROUP_TOP_APP);
     42         super.run();
     43     }
     44 
     45     private static void ensureThreadLocked() {
     46         if (sInstance == null) {
     47             sInstance = new UiThread();
     48             sInstance.start();
     49             final Looper looper = sInstance.getLooper();
     50             looper.setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
     51             looper.setSlowDispatchThresholdMs(SLOW_DISPATCH_THRESHOLD_MS);
     52             sHandler = new Handler(sInstance.getLooper());
     53         }
     54     }
     55 
     56     public static UiThread get() {
     57         synchronized (UiThread.class) {
     58             ensureThreadLocked();
     59             return sInstance;
     60         }
     61     }
     62 
     63     public static Handler getHandler() {
     64         synchronized (UiThread.class) {
     65             ensureThreadLocked();
     66             return sHandler;
     67         }
     68     }
     69 }
     70