sdk3.0前,使用内部的线程池,多线程并发运行。线程池大小等于5,最大达128
sdk3.0后,使用默认的serial线程池。运行完一个线程,再顺序运行下一个线程。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,默觉得 Serial 线程池
public static final Executor SERIAL_EXECUTOR = new SerialExecutor();
public static final Executor THREAD_POOL_EXECUTOR
= new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE,
TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory);
private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR;
public static void setDefaultExecutor(Executor exec) {//设置默认线程池
sDefaultExecutor = exec;
}
SerialExecutor ,使用同步锁,一次运行一个线程
private static class SerialExecutor implements Executor {
final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>();
Runnable mActive;
public synchronized void execute(final Runnable r) {
mTasks.offer(new Runnable() {
public void run() {
try {
r.run();
} finally {
scheduleNext();
}
}
});
if (mActive == null) {
scheduleNext();
}
}
protected synchronized void scheduleNext() {
if ((mActive = mTasks.poll()) != null) {
THREAD_POOL_EXECUTOR.execute(mActive);
}
}
}
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); //能够自己定义 线程池 使用这两种方法