Radio Streaming App Stops When Android Goes To Sleep

Hi all!

I created a super simple Android app for my radio stream that is comprised of the following tiny block:

Now my issue is, everything works, but if I flip the phone's cover, essentially putting it to 'sleep', the stream also stops. I suspect that I am missing something dreadfully obvious and I would be greatly obliged to anyone who could point out what that is! My end goal is for someone to have the phone in their pocket with their ear buds in and the music playing non-stop.

Thanks in advance for looking into this!

Please search the community, this subject has been covered several times....