snackbar action (kotlin)

package com.example.firstapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import androidx.coordinatorlayout.widget.CoordinatorLayout
import com.google.android.material.snackbar.Snackbar

class MainActivity : AppCompatActivity() {

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

        // this part
        val btn = findViewById<Button>(R.id.button) // getting reference of button
        btn.setOnClickListener{
            // getting reference of layout
            val coordinatorLayout = findViewById<CoordinatorLayout>(R.id.coordinatorLayout)
            // setting snackbar
            val snackbar = Snackbar.make(coordinatorLayout, "This is snackbar!", Snackbar.LENGTH_SHORT)
            // adding a button(Undo) in snackbar and setting action if it is clicked
            snackbar.setAction("Undo") {
                // showing another snackbar if the button of previous snackbar is clicked
                Snackbar.make(coordinatorLayout, "Undo action", Snackbar.LENGTH_SHORT).show()
            }
            // showing the snackbar
            snackbar.show()
        }
    }
}