How to observe lifecycle events (onCreate(), onResume(), onStart(),
etc)

Owner CompositionLocal can provide the current LifecycleOwner.

Here we have a username field and a button that enables when the username is valid.

It starts off empty and so our state is false. Now when the user starts typing, our state correctly updates and our button becomes enabled.

This is where derivedStateOf comes in. Our state is changing more than we need our UI to update and so derivedStateOf can be used for this to reduce the number of recompositions.

It acts similarly to the Kotlin Flows distinctUntilChanged() operator.