content: /*
   * Copyright (C) 2013 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;
  
  import android.os.Handler;
  import android.os.Looper;
  import android.os.Process;
  import android.os.Trace;
  
  /**
   * Shared singleton thread for showing UI.  This is a foreground thread, and in
   * additional should not have operations that can take more than a few ms scheduled
   * on it to avoid UI jank.
   */
  public final class UiThread extends ServiceThread {
      private static final long SLOW_DISPATCH_THRESHOLD_MS = 100;
      private static final long SLOW_DELIVERY_THRESHOLD_MS = 200;
      private static UiThread sInstance;
      private static Handler sHandler;
  
      private UiThread() {
          super("android.ui", Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
      }
  
      @Override
      public void run() {
          // Make sure UiThread is in the fg stune boost group
          Process.setThreadGroup(Process.myTid(), Process.THREAD_GROUP_TOP_APP);
          super.run();
      }
  
      private static void ensureThreadLocked() {
          if (sInstance == null) {
              sInstance = new UiThread();
              sInstance.start();
              final Looper looper = sInstance.getLooper();
              looper.setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
              looper.setSlowLogThresholdMs(
                      SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
              sHandler = new Handler(sInstance.getLooper());
          }
      }
  
      public static UiThread get() {
          synchronized (UiThread.class) {
              ensureThreadLocked();
              return sInstance;
          }
      }
  
      public static Handler getHandler() {
          synchronized (UiThread.class) {
              ensureThreadLocked();
              return sHandler;
          }
      }
  }
  