This application is a useless (i.e. unproductive) button that tells the user they have pressed the button when they press it. This was a trial of using Android Studio, Firebase, Notification services, and Ad services together.
To use this application, you can choose one of two options: to clone from GitHub, or to download the release package. Either option will require you, however, to start a Firebase project (with Analytics, App Indexing, Cloud Messaging, In-App Messaging, and AdMob), add the google-services.json file from Firebase to the /app folder, and run the application on some Android device/ emulator.
As this application was mostly an experiment, I have not published it on Google Play Store, which means that the install process may be more cumbersome, but also that the ad monetization was for practice, rather than for any practical income.