Android apps that run continuously in the background are called persistent apps. This ensures that the application is always running and receives and notifies you of messages when they come in.
The first step we need to do is enable debugging settings in the app. To do this click the three vertical line button in the top left corner of your app which will bring up this menu.
You will need to press and hold on the icon that has your initials, or your profile picture, in this case where it say BTS, until you see a message on your screen that will say "Debug Settings Enabled". Once they are enabled you will be presented with this screen:
On this screen press the Power link which will show this menu:
Tap the slider to enable Persistent app.
Your Android app will now be continually running in the background.