Activity Lifecycle is one of the earliest Android apps I wrote, to allow me to see the lifecycle callbacks, in the order they happen.
Questions you could ask are:
What happens when the device is rotated?
What happens when switching between apps?
What difference is there, when switching between activities, if you enable “Don’t keep activities” in the developer options?
Is onActivityResult(…) called before, between or after onStart(…) and onResume(…)?
And many more.
It was originally written in Java and then converted to Kotlin. It was my first adventure with RecyclerView, Crashlytics, AdMob, Dagger, Google Analytics, Firebase Analytics, Ads and Crash Reporting.