Question

我在 Android 中有一个 AsyncTask ，它在另一个线程上运行异步任务（我没有关注线程生活，但我可以给回调到任务）。有没有办法等待异步任务完成调用 Asynctask 的 postExecute 函数？

谢谢，

Answer 1

我认为你应该在这里做的是定义一个AsyncTask接口，将实现该监听器的对象的引用传递给onPostExecute，并从// this is your interface // create it in its own file or as an inner class of your task public interface OnTaskFinishListener { public void onTaskFinish(); } // add the following code to your task's class private OnTaskFinishListener mOnTaskFinishListener; public void setOnTaskFinishListener(OnTaskFinishListener listener) { mOnTaskFinishListener = listener; } // in your onPostExecute method call this listener like this // this will call the implemented method on the listener that you created if (mOnTaskFinishListener != null) { mOnTaskFinishListener.onTaskFinish(); } // suppose this is where you start your task MyBackgroundTask task = new MyBackgroundTask(); // set new listener to your task - this listener will be called // when onPostExecutes completed -> that's what you need task.setOnTaskFinishListener(new OnTaskFinishListener() { @Override public void onTaskFinish() { // implement your code here } }); task.execute(); // and start the task调用该对象的方法。

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Answer 2

我宁愿不实施忙碌的等待策略。两个AsyncTask都可以共享一个Semaphore来保持一个停止，而另一个完成

初始化你的信号量

 private final Semaphore semaphore = new Semaphore(0);

将该对象传递给两个任务

 public AsyncTask1(Semaphore semaphore){
     this.semaphore= semaphore;
 } 

 doInBackground(){
     //do something
     semaphore.acquire(); // <- Waiting till the other task finises
 }

和Task2

 public AsyncTask2(Semaphore semaphore){
     this.semaphore= semaphore;
 } 

 onPostExecute(){
   //do something
   semaphore.release();
}

Answer 3

任务1

   private final Callback callback;
   public AsyncTask1(Callback callback){
       this.callback = callback;
   } 
   doInBackground(){
       //do something
       while(!callback.isFinished()){
           Thread.sleep(WAIT_TIME);
       }
   }

任务2

   private final Callback callback;
   public AsyncTask2(Callback callback){
       this.callback = callback;
   } 
   onPostExecute(){
       //do something
       callback.setFinished(true);
   }

class Callback{
    private volatile boolean finished = false;
    public void setFinished(boolean finished){
        this.finished = finished;
    }
}

在android中的asynctask中等待异步任务

3 个答案: