FabulousFragmentWithFormerCallback.kt

interface FabulousListener {
    fun onClick()
}

class FabulousFragment : Fragment() {

    companion object {
        fun newInstance() = FabulousFragment()
    }

    var listener: FabulousListener? = null
  
    override fun onAttach(context: Context) {
        super.onAttach(context)
        if (context is FabulousListener) {
            listener = context
        } else {
            throw ClassCastException("$context must implement FabulousListener")
        }
    }
   
}