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.HandlerExecutor;
  import android.os.Looper;
  import android.os.Trace;
  
  import java.util.concurrent.Executor;
  
  /**
   * Shared singleton foreground thread for the system.  This is a thread for regular
   * foreground service operations, which shouldn't be blocked by anything running in
   * the background.  In particular, the shared background thread could be doing
   * relatively long-running operations like saving state to disk (in addition to
   * simply being a background priority), which can cause operations scheduled on it
   * to be delayed for a user-noticeable amount of time.
   */
  public final class FgThread extends ServiceThread {
      private static final long SLOW_DISPATCH_THRESHOLD_MS = 100;
      private static final long SLOW_DELIVERY_THRESHOLD_MS = 200;
  
      private static FgThread sInstance;
      private static Handler sHandler;
      private static HandlerExecutor sHandlerExecutor;
  
      private FgThread() {
          super("android.fg", android.os.Process.THREAD_PRIORITY_DEFAULT, true /*allowIo*/);
      }
  
      private static void ensureThreadLocked() {
          if (sInstance == null) {
              sInstance = new FgThread();
              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());
              sHandlerExecutor = new HandlerExecutor(sHandler);
          }
      }
  
      public static FgThread get() {
          synchronized (FgThread.class) {
              ensureThreadLocked();
              return sInstance;
          }
      }
  
      public static Handler getHandler() {
          synchronized (FgThread.class) {
              ensureThreadLocked();
              return sHandler;
          }
      }
  
      public static Executor getExecutor() {
          synchronized (FgThread.class) {
              ensureThreadLocked();
              return sHandlerExecutor;
          }
      }
  }
  