Android Async task cancel/stop

Question

I want to know what is the best way to stop an async task frm running.

I have tried

@Override protected void onCancelled() { 
      super.onCancelled(); 
      mTask.cancel(true);       
 }

I also tried

asyncTaskObject.cancel(true);

This works specially when associated with an event.

But suppose the scenario is--- there are 4 AsyncTask. First call the second, second calls the third and third calls fourth. When the user enters the activity there is no dialogbox. Otherwise we could have used the onCancel method there. When user clicks on anywhere on the page the dialog box appears if user does not click anywhere then no dialog box is shown but async task keep running in the background.Suppose the user clicks the "back" button on or the navigational icon to the home page user.is taken out of the current activity. But the async task keep running in the background and eventually the app crashes. I have used to the cancel method in onBackPressed. But the problem is you cannot be sure which task is running and app carshes again.

What is the way out of this?

score 19 · Accepted Answer · edited Feb 20 '16 at 20:23

19

keep reference to AsyncTask object as instance variable and then in onDestroy() do this

@Override
protected void onDestroy() {
    if (mTask != null) {
        mTask.cancel(true);
    }

    super.onDestroy();
}

edited Feb 20 '16 at 20:23

Jared Burrows

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answered Nov 27 '12 at 13:18

Abhishek Chauhan

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score 4 · Answer 2 · answered Nov 27 '12 at 13:24

In http://developer.android.com/reference/android/os/AsyncTask.html there's a session called Threading rules that say that AsyncTasks instances must be created on the UI thread and execute must be invoked on the UI thread. If you invoke execute from the UI thread you can cancel the thread calling yourTaskInstance.cancel(true);

score 0 · Answer 3 · answered Nov 27 '12 at 13:22

I am not entirely sure when you want to cancel your tasks, but here are a few suggestions: a) keep a reference to each task that is running. b) add a dismiss listener to your dialog and cancel all tasks there (if that's what you want to do). c) cancel all tasks at the onStop callback of your activity (if that's what you want to do again).

Android Async task cancel/stop

3 Answers3