How to display text in Status Bar?

Question

Java

Hello.
There was a question that I can not solve on my own.
I installed Telegram X and noticed in it the output of notifications about searching for a network in the status bar, I decided to find out how this was implemented, but it did not lead to anything.

Screenshots of what it looks like when using Telegram X

Answer 1

B overlay window, I suppose, painted. It is not necessary so, it is not typical for android applications.