android: how to make sure my app doesnt get paused when running in the background

Question

Android app that I am working on reads from near by beacons(devices) using bluetooth. It works fine when the app is in the foreground (tested it for 20 minutes). However, few minutes after app goes to background it stops reading.

I notice when app goes to background, onpause() method is executed; still my app reads for few minutes and then simply stops reading anything (when I manually bring the app to foreground, oncreate method is executed and app continuous normally).

Why is my app stopped reading few minutes after it went to background. My app is an activity and not service.

1. should convert the activity to service or
2. should I create intentservice or
3. should I create foregroundserive

I donot understand the difference between above 3 types of services and if any of them would help me.

Though slightly older threads, I reviewed Prevent that the app get stopped or paused by the OS and How can we prevent a Service from being killed by OS? and my app killed by android system when it running in background

But I am lost. Any discussion is appreciated

EDIT

As I understand from @davidgyoung answer, I have to write a service. I assume GUI portion of my app goes into mainactivity; then how I can ensure my mainactivity/GUI is still active in memory and was not killed by Android by the time service tries to broadcast/notify GUI

/EDIT

Answer 1

An Activity is not designed to run for long periods in the background. The Android OS will destroy activities that are not visible as memory is needed for other functions. While a Service is the proper alternative, even a service will be destroyed under memory pressure by the OS, so you still need to restart the service if it is killed by the OS and you continue to want to do beacon scanning.

All of these issues came up when we built the Android Beacon Library, and we settled on these solutions to keep scanning going:

• Use a Service to scan for beacons in the background. It does not have to be an IntentService, but that is a reasonable option.

• Use an AlarmManager to restart the scanning service 5 minutes in the future in case it gets killed. (This delay allows the OS to time to recover from a temporary need for extra memory.) If the scanning service is still running, just reschedule the alarm.

• Register for OS level events (boot, power connect/disconnect) to restart the scanning service at a later time if the user kills the app with the task switcher.

All of this is built for you if you decide to use the Android Beacon Library (and we welcome contributions, too!) If you want to roll your own, you may want to look at the source code to see how these things were built. Feel free to copy and modify, too. That's the beauty of open source!

Full disclosure: I am the lead developer on the Android Beacon Library open source project.