I could not connect recyclerview with adapter in fragment

Question

the adapter does not connect with recyclerview in fragment

enter code here  override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    recycler?.layoutManager = LinearLayoutManager(this.context,RecyclerView.VERTICAL,false)

    var customAdapter = Custom_Adapter() // error msg : Unresolved reference
    recycler?.adapter = customAdapter


}