How to keep activity running in background? [duplicate]

Answer 1

It's not the Activity that keeps running in the background but a Service. Look at http://developer.android.com/reference/android/app/Service.html for implementing it.

Answer 2

Use service. Read this and this about details of service.

You can keep your activity running in the background. But I think it is definitely a better idea to keep a service running in the background. You will get a basic idea about the service by reading above two links.