转载自：http://blog.csdn.net/jjwwmlp456/article/details/38623563
sdk3.0前，使用内部的线程池，多线程并发执行。线程池大小等于5，最大达128
sdk3.0后，使用默认的serial线程池，执行完一个线程，再顺序执行下一个线程。sdk3.0<=current version <= sdk4.3时 线程池大小等于5，最大达128
sdk4.4后线程池大小等于 cpu count + 1，最大值为cpu count * 2 + 1
sdk3.0后有两种线程池的实现，默认为 Serial 线程池
1 public static final Executor SERIAL_EXECUTOR = new SerialExecutor(); 2 public static final Executor THREAD_POOL_EXECUTOR 3 = new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, 4 TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory); 5 private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR; 6 public static void setDefaultExecutor(Executor exec) {//设置默认线程池 7 sDefaultExecutor = exec; 8 }
SerialExecutor ，使用同步锁，一次执行一个线程
1 private static class SerialExecutor implements Executor { 2 final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>(); 3 Runnable mActive; 4 5 public synchronized void execute(final Runnable r) { 6 mTasks.offer(new Runnable() { 7 public void run() { 8 try { 9 r.run(); 10 } finally { 11 scheduleNext(); 12 } 13 } 14 }); 15 if (mActive == null) { 16 scheduleNext(); 17 } 18 } 19 20 protected synchronized void scheduleNext() { 21 if ((mActive = mTasks.poll()) != null) { 22 THREAD_POOL_EXECUTOR.execute(mActive); 23 } 24 } 25 }
THREAD_POOL_EXECUTOR 并发线程池
asynctask.setDefaultExecutor(AsyncTask.THREAD_POOL_EXECUTOR); //设置使用 并发线程池
//params 都是使用在doInBackground(Params... params);
asynctask.executeOnExecutor(executor, params); //可以自定义 线程池 使用这两种方法
