Android service Life cycle

A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use.Android also provides services to facilitate the user and emphasizes the need to understand the services life cycle.



                                                     Android Service Lifecycle
The lifecycle for a service is similar to that for an activity, but different in a few important details:

onCreate and onStart differences

Services can be started when a client calls the Context.startService(Intent)
method. If the service isn’t already running, Android starts it and calls its
onCreate method followed by the onStart method. If the service is already running,
its onStart method is invoked again with the new intent. So it’s quite possible and
normal for a service’s onStart method to be called repeatedly in a single run of the
service.

onResume, onPause, and onStop are not needed

Recall that a service generally has no user interface, so there isn’t any need for the
onPause, onResume, or onStop methods. Whenever a service is running, it is always
in the background.

onBind

If a client needs a persistent connection to a service, it can call the Context.bind
Service method. This creates the service if it is not running, and calls onCreate but
not onStart. Instead, the onBind method is called with the client’s intent, and it
returns an IBind object that the client can use to make further calls to the service.
It’s quite normal for a service to have clients starting it and clients bound to it at
the same time.

onDestroy

As with an activity, the onDestroy method is called when the service is about to be
terminated. Android will terminate a service when there are no more clients starting
or bound to it. As with activities, Android may also terminate a service when
memory is getting low. If that happens, Android will attempt to restart the service
when the memory pressure passes, so if your service needs to store persistent information
for that restart, it’s best to do so in the onStart method.