SendBroadcast if activity or notification

I have an application that is downloading data in the background and I want to be able to update the activity's UI if they are currently launching the application or trigger a notification if they are not.

How do I know if an app is in the foreground?

I can register the internal BroadcastReceiver class in an activity and fire it if its in the foreground otherwise uses a notification, but I don't know how I can check what action to take.

Thanks for any answers.