What is the easiest-quickest way to write an android app with uart access?

Question

Android

I need an android application with a slider on the screen, which, when the slider is moved, sends the value of this slider to the usb-otg uart (com port) (for example, 0-255). Offer a set of development tools, and other components with which it is possible to do this. We also welcome the advice of ready-made applications for android with plugins for the tasker, which implement the ability to send arbitrary numbers to the usb uart adapter

Answer 1

Android Studio, I recommend kotlin as a language and read about uart here https://developer.android.com/things/sdk/pio/uart

Answer 2

In android for USB it's easy to work with bulkTransfer only.
There are no normal libs for working with USB-COM converters.
Nobody updated the library from Google for 8 years.
And it worked with 3 or 4 specific chips.