It's usually a better idea not to code for a specific window size, but to code the gui in such a way that regardless of the window size it tries to do something sensible. For instance, your app might have a navigation bar at the top that is always 40dp high, then the rest of the app is taken up by something else that grows to fill all the available space.
You can code the whole gui to a fixed size if you want of course, but it probably isn't the best solution.
I am coding kivy app on PC. At the end, I will convert it to .apk on my android phone (redmi note 9 pro). Which window size should I choose? It will be easier to code with this specific window size (add buttons and text on specific place).
And how to do it. Because I heard that using window.size is not good/not working.
Thanks
Kivy window size for mobile