How to start working on async task in one activity and inform another activity on completion of work in OnBackground

Question

I would like to achieve the following behaviour, but I\'m not sure how:

   1. User start an activity
   2. Activity starts an AsyncTask
   3. After initiating th         


        

Answer 1

• Create BroadcastReceiver in second activity and register it using registerReceiver() method.

• sendBroadcast() in AsyncTask onPostExecute() method of first Activity.

  public class SecondActivity extends Activity {
      private BroadcastReceiver myBroadcastReceiver =
          new BroadcastReceiver() {
              @Override
              public void onReceive(...) {
                  ...
              }
         });
  
      ...
  
      public void onResume() {
          super.onResume();
          IntentFilter filter = new IntentFilter();  
                      filter.addAction("com.example.asynctaskcompleted");  
                      filter.addCategory("android.intent.category.DEFAULT");
          registerReceiver(myBroadcastReceiver, filter);
      }
  
      public void onPause() {
          super.onPause();
          ...
          unregisterReceiver(myBroadcastReceiver);
      }
      ...
  }
  
  
  public class FirstActivity extends Activity {
      private class MyTask extends AsyncTask<Void, Void, Void> {
          protected Void doInBackground(Void... args) {
          ...
      }    
  
      protected void onPostExecute(Void result) {
          Intent intent = new Intent ("com.example.asynctaskcompleted");            
  
          FirstActivity.this.sendBroadcast(intent);
   }
  

  }

Answer 2

You can create interface, pass it to the AsyncTask (in constructor), and then call interface method in onPostExecute..and make your second activity implements this interface..

For example:

Your interface:

public interface OnTaskCompleted {
    void onTaskCompleted();
}

Your second Activity:

public MyActivity implements OnTaskCompleted {
    //your Activity
}

And your AsyncTask:

public YourTask extends AsyncTask<Object,Object,Object> { //change Object to required type
    private OnTaskCompleted listener;

    public YourTask(OnTaskCompleted listener) {
        this.listener=listener;
    }

    //required methods

    protected void onPostExecute(Object o) {
        //your stuff
        listener.onTaskCompleted();
    }
}