How to properly initialize a Listener in an Activity?

Question

Java

Good afternoon, there was a task to throw the Listener from the Fragment into the Activity. With the reverse task, everything is simple. I just implement the callback methods onAttach and onDetach. But how to do the opposite? More precisely, how to do it right?

override fun onAttach(context: Context) {
        super.onAttach(context)
        if(context is OnCityChangeListener) {
            listener = context
        }
    }

    override fun onDetach() {
        super.onDetach()
        listener = null
    }

Answer 1

I would implement using EventBus, both ways

Answer 2

Make a ListenerHolder interface with add/removeListener methods, implement it in an activity. In the fragment, cast an activity to this interface and poke yourself into it.