Window on top of all windows - how?

Question

Android

Because I only coded in web (php). In android there was no experience yet, I'm studying.
The question is the following. How to make a window on top of all others?
Those. wherever the user is, in the launcher, in a windowed or full-screen application. I want to display on top of all windows continuously - for example time or other information.
In short, how can this be done? What will need to be studied? Is this all done in Android Studio or would something more magical be required?

Answer 1

Is this all done in Android Studio or would something more magical be required?

of course you need something magical, for example java

Answer 2

Better in the notification area. You can display an arbitrary widget there with your own buttons and fields.