code: private void setCurrentForegroundActivity(Activity activity) {
  		if (activity != null) {
  			currentForegroundApptentiveActivity = new WeakReference<>(activity);
  		} else {
  			ApptentiveToastNotificationManager manager = ApptentiveToastNotificationManager.getInstance(null, false);
  			if (manager != null) {
  				manager.cleanUp();
  			}
  			currentForegroundApptentiveActivity = null;
  		}
  	}
docs: Set when Activity.onStart() and onStop() are called