Your service is now running and doing its thing in the background. But the user never knows a thing about it, so it is not worth much.
When your service needs to communicate something to the user, the proper tool is almost always a notification. Notifications are items that appear in the notifications drawer, which the user can access by dragging it down from the top of the screen.
To post a notification, you first need to create a Notification object. Notifications are created by using a builder object, much like the AlertDialog that you used in Chapter 12. At a minimum, your Notification should have:
ticker text to display in the status bar when the notification is first shown on pre-Lollipop devices (starting ...