Android 无法将片段中的 recyclerview 与适配器连接

我的片段类

class RecyclerFragment : Fragment() {
var recycler:RecyclerView? =null

private var param1: String? = null
private var param2: String? = null


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    recycler = view?.findViewById(R.id.recycler)

    }


override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_recycler, container, false)
}

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


    recycler?.adapter = Custom_Adapter() // error-Unresolved reference: Custom_Adapter


}


}

//这是我的adater

 class Custom_Adapter() : RecyclerView.Adapter<Custom_Adapter.ViewHolder>() {


override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): Custom_Adapter.ViewHolder {
 var myViewInflater = LayoutInflater.from(viewGroup.context).inflate(R.layout.custom_layout,viewGroup,false)
    return ViewHolder(myViewInflater)
}

override fun onBindViewHolder(holder: Custom_Adapter.ViewHolder, position: Int) {

}

override fun getItemCount(): Int {
    return 9

}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

}
}