Too opened question I think ?
You encapsulate:

Install kivy
Write your program
Deploy it

I suppose you want to focus on how to program it and you will manage to learn how to install and deploy it.
I suppose that you want to use the phone's camera to analyse the barcode.
I have an application that need to take photos and analyze the text on it to write it in a form. I didn't manage to make it work personnaly. Try to know if the kivy cam is "stable enough" to allowed saving/loading/real_time_analyze on Android.
If you manage to make your camera work, you will need to focus on the analyse of the barcode. I think that you can reuse working library and use it on your application (or on a AWS lambda as a micro-service).
I salute all brethren here. Please I was tasked by my superior in a pharmacy outlet to generate barcode taking into consideration drug's country of origin ID or code, supplier code, product code and product classification as in pain killer etc. All these must be serialize into a readable barcode. So it means this must link to a database. Please brethren, how do I go about this in python kivy?
Barcode with kivy