Overriding back button in fragments was never this easy!

FragmentExtensions.kt

fun Fragment.overrideBackButtonWith(block: () -> Unit) {
    requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner,
        object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                block()
                remove() // remove this back button handler
            }
        })
}

As an usage example, let's assume we have an Contextual ActionBar and when activiated we want back button to cancel contextual mode

// inside a fragment
// change toolbar/actionbar to contextual
overrideBackButtonWith {
    // end the contextual mode
}