talk/examples/android/src/org/appspot/apprtc/util/LooperExecutor.java

/*
 * libjingle
 * Copyright 2015 Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.appspot.apprtc.util;

import android.os.Handler;
import android.os.Looper;
import android.util.Log;

import java.util.concurrent.Executor;

/**
 * Looper based executor class.
 */
public class LooperExecutor extends Thread implements Executor {
  private static final String TAG = "LooperExecutor";
  // Object used to signal that looper thread has started and Handler instance
  // associated with looper thread has been allocated.
  private final Object looperStartedEvent = new Object();
  private Handler handler = null;
  private boolean running = false;
  private long threadId;

  @Override
  public void run() {
    Looper.prepare();
    synchronized (looperStartedEvent) {
      Log.d(TAG, "Looper thread started.");
      handler = new Handler();
      threadId = Thread.currentThread().getId();
      looperStartedEvent.notify();
    }
    Looper.loop();
  }

  public synchronized void requestStart() {
    if (running) {
      return;
    }
    running = true;
    handler = null;
    start();
    // Wait for Hander allocation.
    synchronized (looperStartedEvent) {
      while (handler == null) {
        try {
          looperStartedEvent.wait();
        } catch (InterruptedException e) {
          Log.e(TAG, "Can not start looper thread");
          running = false;
        }
      }
    }
  }

  public synchronized void requestStop() {
    if (!running) {
      return;
    }
    running = false;
    handler.post(new Runnable() {
      @Override
      public void run() {
        Looper.myLooper().quit();
        Log.d(TAG, "Looper thread finished.");
      }
    });
  }

  // Checks if current thread is a looper thread.
  public boolean checkOnLooperThread() {
    return (Thread.currentThread().getId() == threadId);
  }

  @Override
  public synchronized void execute(final Runnable runnable) {
    if (!running) {
      Log.w(TAG, "Running looper executor without calling requestStart()");
      return;
    }
    if (Thread.currentThread().getId() == threadId) {
      runnable.run();
    } else {
      handler.post(runnable);
    }
  }

}