It's an aplication build with Kotlin as an example on how to display data from a Fireabse Realtime Database, using three different approaches. The first approach is using a callback, the second approach is using an Android Architecture Component called LiveData, and the third one is using Kotlin Coroutines. All three approaches are using the same Android Architecture Component called ViewModel.
To keep things simple, the app uses a very simple database schema that look like in the image below:
To make this app work, follow the instructions given in the official documentation regarding how to add Firebase to your project. Add the JSON file in your app folder, add some dummy products and see it working.
This repo is the source code of the this article: How to read data from Firebase Realtime Database using get()?
See it also on youtube: https://youtu.be/mOB40wowo6Y