BottomSheetDialogFragment - listen to dismissed by user event

Question

How can I listen to a FINAL dismissal of a BottomSheetDialogFragment? I want to save user changes on the final dismissal only...

I tried following:

Answer 1

In an AppCompatActivity you can use the following technique:

    val mgr = supportFragmentManager
    val callback = object: FragmentManager.OnBackStackChangedListener {
        var count = 0
        override fun onBackStackChanged() {
            // We come here twice, once when the sheet is opened, 
            // once when it's closed.
            if (++count >= 2) {
                mgr.removeOnBackStackChangedListener(this)
                doWhatNeedsToBeDoneWhenTheSheetIsClosed()
            }
        }
    }
    mgr.addOnBackStackChangedListener(callback)

Be sure to do the above just before you call show on the sheet.