Android之AsyncTask两种线程池分析和总结
【摘要】 Android AsyncTask两种线程池分析和总结
(一) 前言
在android AsyncTask里面有两种线程池供我们调用
1． THREAD_POOL_EXECUTOR, 异步线程池
2． SERIAL_EXECUTOR，同步线程池
正如上面名称描述的那样，一个是异步线程池，多...
(二) THREAD_POOL_EXECUTOR用法举例
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private static int produceTaskMaxNumber = 500;
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public void dotask(){
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for (int i = 1; i <= produceTaskMaxNumber; i++){
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// 产生一个任务，并将其加入到线程池
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String task = "task@ " + i;
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Log.d("Sandy", "put " + task);
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MyAsyncTask asynct = new MyAsyncTask(task);
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asynct.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 0);
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}
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}
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static class MyAsyncTask extends AsyncTask<Integer, Integer, Integer>{
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private static int consumeTaskSleepTime = 2000;
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// 保存任务所需要的数据
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private Object threadPoolTaskData;
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public MyAsyncTask(String s){
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threadPoolTaskData = s;
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}
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<a href="http://home.51cto.com/index.php?s=/space/5017954" target="_blank">@Override</a>
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protected Integer doInBackground(Integer... arg0) {
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Log.d("Sandy", "start .." + threadPoolTaskData
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+ " thread id: " + Thread.currentThread().getId()
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+ " thread name: " + Thread.currentThread().getName());
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try {
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// //便于观察，等待一段时间
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Thread.sleep(consumeTaskSleepTime);
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}
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catch (Exception e) {
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Log.d("Sandy", "", e);
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}
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threadPoolTaskData = null;
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return 0;
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}
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}
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MyAsyncTask asynct = new MyAsyncTask(task);
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asynct.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, 0);
就是因为我们尝试添加500个task到AsyncTask.THREAD_POOL_EXECUTOR线程池中，但是它的核心线程是5，队列容量是128，最大线程数是9。
所以，抛出了这个异常。
那么，接下来的话，我们会去分析这个异常怎么出来的。
(三) THREAD_POOL_EXECUTOR代码分析
从AsyncTask.THREAD_POOL_EXECUTOR的定义开始分析
1. 代码路径
frameworks\base\core\java\android\os\AsyncTask.java
代码：
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private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors();
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private static final int CORE_POOL_SIZE = CPU_COUNT + 1;
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private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1;
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private static final int KEEP_ALIVE = 1;
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....
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/**
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* An {@link Executor} that can be used to execute tasks in parallel.
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*/
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public static final Executor THREAD_POOL_EXECUTOR
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= new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE,
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TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory);
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public ThreadPoolExecutor(int corePoolSize,
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int maximumPoolSize,
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long keepAliveTime,
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TimeUnit unit,
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BlockingQueue<Runnable> workQueue,
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ThreadFactory threadFactory,
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RejectedExecutionHandler handler) {
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if (corePoolSize < 0 ||
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maximumPoolSize <= 0 ||
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maximumPoolSize < corePoolSize ||
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keepAliveTime < 0)
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throw new IllegalArgumentException();
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if (workQueue == null || threadFactory == null || handler == null)
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throw new NullPointerException();
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this.corePoolSize = corePoolSize;
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this.maximumPoolSize = maximumPoolSize;
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this.workQueue = workQueue;
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this.keepAliveTime = unit.toNanos(keepAliveTime);
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this.threadFactory = threadFactory;
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this.handler = handler;
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}
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/**
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* The default rejected execution handler
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*/
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private static final RejectedExecutionHandler defaultHandler =
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new AbortPolicy();
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a. asynct.executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, 0); |
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b. asynct.execute(0); |
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public final AsyncTask<Params, Progress, Result> executeOnExecutor(Executor exec, |
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Params... params) { |
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... |
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exec.execute(mFuture); |
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.... |
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} |
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private static class SerialExecutor implements Executor { |
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final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>(); |
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Runnable mActive; |
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public synchronized void execute(final Runnable r) { |
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mTasks.offer(new Runnable() { |
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public void run() { |
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try { |
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r.run(); |
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} finally { |
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scheduleNext(); |
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} |
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} |
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}); |
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if (mActive == null) { |
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scheduleNext(); |
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} |
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} |
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protected synchronized void scheduleNext() { |
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if ((mActive = mTasks.poll()) != null) { |
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THREAD_POOL_EXECUTOR.execute(mActive); |
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} |
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} |
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} |
文章来源: chenyu.blog.csdn.net，作者：chen.yu，版权归原作者所有，如需转载，请联系作者。
原文链接：chenyu.blog.csdn.net/article/details/50494611
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