如何在AsyncTask doInBackground（）中使用同步对象？

Posted 2021-05-02

我在后台线程中使用synchronized对象时遇到了麻烦。我在样本简介中指定了问题：

1. 我写这样简单的类： public class UIThreadClass { MyObject object; UIThreadClass() { object = new MyObject(); object.doActionOne(); object.doActionTwo(); } }
2. 现在我的任务是通过将两个方法放到非UI线程来改进代码。我正在使用AsyncTask 对于doActionOne（） private static class DoActionOneTask extends AsyncTask<Void, Void, Void> { private WeakReference<MyObject> wObject; DoActionOneTask(MyObject object) { wObject = new WeakReference<>(object); } @Override protected Void doInBackground(Void... voids) { if(wObject.get() != null) { MyObject myObject = wObject.get(); myObject.doActionOne(); } return null; } } 对于doActionTwo（） private static class DoActionTwoTask extends AsyncTask<Void, Void, Void> { private WeakReference<MyObject> wObject; DoActionOneTask(MyObject object) { wObject = new WeakReference<>(object); } @Override protected Void doInBackground(Void... voids) { if(wObject.get() != null) { MyObject myObject = wObject.get(); myObject.doActionTwo(); } return null; } } 现在在UI线程中调用它们 public class UIThreadClass { MyObject object; UIThreadClass() { object = new MyObject(); new DoActionOneTask(object).execute(); new DoActionTwoTask(object).execute(); } }

问题是：

使用AsyncTask时 - 如何同步对象以确保在doActionOne（）方法之后总是调用doActionTwo（）？

我尝试在doInBackground（）中使用synchronized（myObject）{myObject.doActionOne（）;}但是系统警告我myObject只是局部变量而且很难保证正确性。

任何人都可以帮我这种情况吗？非常感谢！

答案

你不需要做任何事情。它们将按照android文档顺序执行

Order of execution
When first introduced, AsyncTasks were executed serially on a single background thread. Starting with DONUT, this was changed to a pool of threads allowing multiple tasks to operate in parallel. Starting with HONEYCOMB, tasks are executed on a single thread to avoid common application errors caused by parallel execution.

If you truly want parallel execution, you can invoke executeOnExecutor(java.util.concurrent.Executor, Object[]) with THREAD_POOL_EXECUTOR.