Kotlin drag to reorder recyclerview

MainActivity.kt

package uk.co.jatra.recorder

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import android.support.v7.widget.helper.ItemTouchHelper
import android.support.v7.widget.helper.ItemTouchHelper.DOWN
import android.support.v7.widget.helper.ItemTouchHelper.UP
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import kotlinx.android.synthetic.main.edit_form.*
import java.util.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.edit_form)

        val myAdapter = MyAdapter(getData())
        recyclerView.adapter = myAdapter
        recyclerView.layoutManager = LinearLayoutManager(this)

        val touchHelper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(UP + DOWN, 0) {
            override fun onMove(recyclerView: RecyclerView?, viewHolder: RecyclerView.ViewHolder?, target: RecyclerView.ViewHolder?): Boolean {
                myAdapter.onItemMove(viewHolder?.adapterPosition, target?.adapterPosition);
                return true
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder?, direction: Int) {
            }

            override fun isLongPressDragEnabled(): Boolean {
                return true
            }
        })

        touchHelper.attachToRecyclerView(recyclerView)

    }

}

class MyAdapter(val data: List<String>) : RecyclerView.Adapter<MyViewHolder>() {

    override fun getItemCount() = data.size

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        (holder.itemView as TextView).text = data[position]
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false)
        return MyViewHolder(view)
    }

    fun onItemMove(fromPosition: Int?, toPosition: Int?): Boolean {
        fromPosition?.let {
            toPosition?.let {
                if (fromPosition < toPosition) {
                    for (i in fromPosition until toPosition) {
                        Collections.swap(data, i, i + 1)
                    }
                } else {
                    for (i in fromPosition downTo toPosition + 1) {
                        Collections.swap(data, i, i - 1)
                    }
                }
                notifyItemMoved(fromPosition, toPosition)
                return true
            }
        }
        return false
    }

}

class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)

private fun getData(): List<String> {
    return listOf(
            "one",
            "two",
            "three",
            "four",
            "five",
            "six",
            "1one",
            "1two",
            "1three",
            "1four",
            "1five",
            "1six",
            "2one",
            "2two",
            "2three",
            "2four",
            "2five",
            "2six",
            "3one",
            "3two",
            "3three",
            "3four",
            "3five",
            "3six",
            "seven"
    )
}