Kotlin class

package com.example.ps_4.sudoku
 
import android.support.v7.app.AppCompatActivity
import android.support.v7.app.ActionBar
import android.os.Bundle
import android.view.Menu;
import android.view.View
import android.widget.Button
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_game.*
 
class Game : AppCompatActivity()  {
 
    val buttonsonbottom : ButtonHandlerOnBottom = ButtonHandlerOnBottom()
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_game)
        gorot.text = "sdfsfds"
        val example : Button = bt_1
    }
}

package com.example.ps_4.sudoku
 
import android.widget.Button
import android.view.View.OnClickListener
import com.example.ps_4.sudoku.R.id.bt_1
import com.example.ps_4.sudoku.R.id.gorot
import com.example.ps_4.sudoku.R.id.*
import com.example.ps_4.sudoku.R.id.gorot
import kotlinx.android.synthetic.main.activity_game.*
 
class ButtonHandlerOnBottom() {
    val bt1 : Button
    val bt2 : Button
    val bt3 : Button
    val bt4 : Button
    val bt5 : Button
    val bt6 : Button
    val bt7 : Button
    val bt8 : Button
    val bt9 : Button
 
    var currentbutton : String
 
    init {
        currentbutton = ""
        //SAM constructor to reuse event handler
        val listener = OnClickListener { view ->
            val text = when(view.id){
                bt_1 -> "1"
                bt_2 -> "2"
                bt_3 -> "3"
                bt_4 -> "4"
                bt_5 -> "5"
                bt_6 -> "6"
                bt_7 -> "7"
                bt_8 -> "8"
                bt_9 -> "9"
                else -> "unknown button"
            }
            gorot.Text = text
            currentbutton = text
        }
 
//       why bt_1 is Int ???????
        bt1 = bt_1
        bt2 = bt_2 as Button
        bt3 = bt_3 as Button
        bt4 = bt_4 as Button
        bt5 = bt_5 as Button
        bt6 = bt_6 as Button
        bt7 = bt_7 as Button
        bt8 = bt_8 as Button
        bt9 = bt_9 as Button
 
        bt1.setOnClickListener(listener)
        bt2.setOnClickListener(listener)
        bt3.setOnClickListener(listener)
        bt4.setOnClickListener(listener)
        bt5.setOnClickListener(listener)
        bt6.setOnClickListener(listener)
        bt7.setOnClickListener(listener)
        bt8.setOnClickListener(listener)
        bt9.setOnClickListener(listener)
    }
}