Question

I have main an Activity class, a broadcast class ( subclass of broadcast receiver ) and few other classes. I use a Handler created in the broadcast class, for some things to do in future. But if some circumstances come ( user wants to exit app ), i want that Handler to cancel (prevent from being executed ).

I read a lot of threads in SO on how to cancel Handlers and I know how to from same class ( Handler.removeCallback (Runnable ), Handler.removeMessages(0) etc ). But I don’t know how to cancel it from my Activity. ( user presses exit button, and if handler is going to do some work i want to prevent that ).

So how do I reference that handler object (which is going to execute ) from the Activity class ?

Answer 1

I’m not sure I fully understand your question, however, if you want to cancel the Handler via an activity, you can put it in the onPause method:

@Override
public void onPause() {
    super.onPause();
    handler.removeCallbacks(runnable);
}

The onPause method is called when an activity is about to be hidden from the user.

Having re-read your question, if you mean that you want to access the handler inside a BroadcastReceiver class from your Activity class, then you should make the handler a member variable of your activity.

public class MyActivity extends Activity {

    private Handler mHandler = new Handler();

    public class BroadcastReceiver mReceiver = new BroadcastReceiver() {

        public void onReceive (Context context, Intent intent) {
            // ... use mHandler in here ....
            mHandler.postDelayed(runnable, 1000);
        }

    }

    // ... rest of the code ...

    @Override
    public void onPause() {
        super.onPause();
        handler.removeCallbacks(runnable);
    }

}

You can use the handler inside your BroadcastReceiver and Activity class using mHandler. You have to make sure that your BroadcastReceiver class is not a static inner class of the Activity.