<How is a Always on Display for Android coded?> My...

# stackoverflow

[user]

How is a Always on Display for Android coded?
My smartphone (Samsung A21s) doesn't supoort the AOD of Samsung. So i tested several apps from the Play store. But I want an app,so i decided to code my own app, which allows me to choose my own background. I want to use the pictures from the gallery. I also want a music control for the AOD. I have a accurate idea of what I want, but I don't know how to code it. Does anybody know, how a AOD is coded? I use Kotlin and I'm working with Android Studio.
Thank you for your help