Make a service run indefinitely and communicate with activity

Question

I Can't understand the differences on android services

I want to have a service run all the time in the background (activity recognition)

When it detect that I RUN -> open GPS -> save curent longitude latitude -> if I stopped to run (WALKING) -> display the log lat on my MainActivity

i want the service run if the user close the app , if the device is closed and re-open , if my service is killed

so I read about:

[Started Service , Intent Service , Bound Service , Intent Bound Service , Job Scheduler , Job Intent Service].......But still i missing something

I understand that with Service start_sticky for API<26 will run forever (if not killed) and with IBinder I can update the UI of my MainActivity; right?

My Many Q are ...:

1. Bound services can run for ever? and update my UI of MainActivity? do i need bound or i can achieve this with service or intent service

2. For oreo I "must" use Job Scheduler -> when killed -> open again with broadcast receiver || work manager || alarm manager ||?

My questions are more for theory Answers not code.

NEED to -> service for "ever" run -> if (something) -> open gps -> save long lat -> show long lat in UI of MainActivity.

Answer 1

To keep a Service running indefinitely in the background, use a foreground service. This will force you to maintain a visible notification/nav bar icon; that's the price Android extracts from you in exchange for keeping your service running for a long time period. Supported on API 5+.

JobScheduler/WorkManager/AlarmManager won't prevent your Service from being killed. They can be used to bring your Service back to life. Also, JobScheduler and WorkManager can get your system out of doze, so you can do useful work. A WakeLock may also be necessary. If the user explicitly terminates your app, JobScheduler jobs will no longer wake it up. I don't know of any good, "Android-approved" way to resuscitate an app in this circumstance. Although, even on Oreo+, you can register to receive these intents, which you can use to regain execution.

You can make any of the Service subclasses you mentioned into a foreground service (by calling startForeground(). The choice of subclass is a matter of convenience, and depends on how you would like to dispatch & schedule your work. Your app could just as easily be implemented with the base-class Service.

START_STICKY doesn't actually prevent a Service from stopping. It's more like a request to the system: "After you kill my app/service, please restart it, if/when you see fit". In my opinion, it is not an effective way of keeping a Service running for a long period of time. If a Service is not in the foreground, and no other application components are in the foreground (e.g., on screen), then Android can kill your app quite quickly. This is more true of later versions of the OS (Oreo+).

Your Service will need to be bound to other components (e.g., Activities) from time to time. You bind to a Service so you can 1.) Make sure it exists and 2.) Carry out communications with it (call functions on it, etc.). So, yes, with IBinder, you can update the UI of your MainActivity.

Binding a Service doesn't make it run forever. If your Activity is bound to the Service, you can be confident that the Service will stick around for as long as the Activity is onscreen. Once it leaves the screen, all bets are off.

In other words, Android is very likely to kill an app/service when it's not in the foreground, and not bound to any components that are in the foreground (onscreen).

A Service can generally open up an Activity at any time it chooses, simply by calling startActivity(). Your Activity can even dismiss the keyguard (in certain circumstances), using FLAG_DISMISS_KEYGUARD.

If you can tolerate less frequent location updates, you may be able to do this without staying in the foreground, but there are limitations.