code: private void registerNotifications() {
  		ApptentiveNotificationCenter.defaultCenter()
  			.addObserver(NOTIFICATION_ACTIVITY_STARTED, this)
  			.addObserver(NOTIFICATION_ACTIVITY_RESUMED, this)
  			.addObserver(NOTIFICATION_APP_ENTERED_FOREGROUND, this)
  			.addObserver(NOTIFICATION_APP_ENTERED_BACKGROUND, this)
  			.addObserver(NOTIFICATION_PAYLOAD_WILL_START_SEND, this)
  			.addObserver(NOTIFICATION_PAYLOAD_DID_FINISH_SEND, this);
  	}
docs: region Notifications