This is a simple app that allows encrypting and decrypting strings with keys stored in private shared preferences. On Android M or newer the keys are further encrypted with a master key stored in Android Keystore.
It demonstrates the basic steps of using Tink, namely generating or loading key material, obtaining a primitive, and using the primitive to do crypto. It also shows how one can add a dependency on Tink using Gradle.
The easiest way to build this app is to import it to Android Studio. You can also build it from the command line.