The purpose of this repository is to demonstrate a problem with a viewTreeObserver obtained from the fragments view during onDestroyView callback. It started happening after updating the androidx.fragment:fragment artifact to version 1.2.0.

1. A OnGlobalLayoutListener is added during onViewCreated callback.
2. The listener is removed during onDestroyView
3. The listener is still being called after onDestroyView - unexpected

This code intentionally crashes the app when the scenario described above happens.

class MainFragment : Fragment() {
    private val onLayoutObserver = ViewTreeObserver.OnGlobalLayoutListener {
        if (view == null) {
            throw IllegalStateException()
        }
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        view.viewTreeObserver.addOnGlobalLayoutListener(onLayoutObserver)
    }

    override fun onDestroyView() {
        super.onDestroyView()
        // this has no effect
        requireView().viewTreeObserver.removeOnGlobalLayoutListener(onLayoutObserver)
    }
}

The scenario above can be fixed using viewTreeObserver obtained from the decorView instead of the fragments view.