Performs the service when no custom view controller is provided.
- iOS 6.0+
The default implementation of this method does nothing. If your service does not provide any custom UI using the
activity method, override this method and use it to perform the activity. Your activity must operate on the data items received in the
This method is called on your app’s main thread. If your app can complete the activity quickly on the main thread, do so and call the
activity method when it is done. If performing the activity might take some time, use this method to start the work in the background and then exit without calling
activity from this method. When your background work has completed, call
activity. You must call
activity on the main thread.