How to change text size in all fragments in mob. application?

Question

Java

Hello everyone, please help. I would like to make a menu, and in the drop-down window, change the text size with one click. Somewhere I saw a lesson, but I didn’t save it, but now I need it and I can’t find it.
Approximately this:

Answer 1

You can use pre-prepared styles (style) and the "setTextSize" parameter