IssueTracker

Component used:

• androidx.activity:activity-ktx:1.4.0
• androidx.fragment:fragment-ktx:1.4.1
• androidx.appcompat:appcompat:1.4.1

Common sense and documentation says:

A fragment's lifecycle state can never be greater than its parent. For example, a parent fragment or activity must be started before its child fragments. Likewise, child fragments must be stopped before their parent fragment or activity.

First, from some weird reason there are two Activity's lifecycle:

• public one accessible through getLifecycle() method
• custom one introduced in FragmentActivity, that is correctly coordinated with fragments state

The public one gets updated to STARTED state after fragments are updated to STARTED. It is because this update is not handled in (Fragment)Activity.onStart, but rather via onActivityPostStarted.

This has great consequences, especially on OnBackPressedDispatcher, which is driven by the STARTED state.

E.g. I have:

• registered back-press callback in Activity with its lifecycle backPressedDispatcher.addCallback(this) {}
• I have startActivityForResult contract in my fragments, when I receive a result, I trigger navigation event which gets processed since Fragment is STARTED. The navigation back calls requireActivity().onBackPressed();
• Back handling is triggered, but since activity is not started yet, its back-press callback is ignored and activity closes.

Note: FragmentManager's back-press callbacks are registered properly with the internal lifecycle since FragmentController receive HostCallbacks with it.