Running a thread while Android app is in foreground

I have an Android app. I have a main activity, that has a button. When the button is clicked, another activity comes to the foreground. The thing is, I want to run a background thread that polls updates from the server. However, I want it to run only when the app is in foreground (either the main activity or the second one), and to stop polling when the user clicks the Home button or clicks the Back button till it's going back from the main activity.

But how do I know if the app is still in the foreground? I can catch the onPause of the main activity, but it's calle开发者_JAVA百科d also when I'm launching the second activity.

So how do I know when the app is in background?

Thanks

You should make a Service for the work you are doing in the background.

For stopping it when you click the Home or Back button, just make a listener for them and stop the Service when either one is pressed.

Seems easiest to me that each activity polls. Is it super important that it can poll when it is between the two activities? Otherwise you will have problems about knowing who is in front or not.

You can have a singleton with reference counting. You main activity should add the first reference on it's onResume and from now, upon calling for every new activity (startActivity for example) you should add a reference. Each activity should decrease the reference counting on its onPause.

Another option is to use services: Services