A bare-bones tip calculator Android app.

This code demonstrates the "classic" approach to Android UI using an Activity
with no Fragment(s)

This kind of app is one notch above "Hello, world". It exists as part of a
collection of open-source projects for instructional purposes, not because
the world actually needs yet another tip calculator. That said, it does serve
a marginally useful purpose and is totally free, with no unnecessary
permissions, no ads, no notification bar spam etc.