toast (kotlin)

package com.example.firstapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.Toast

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)
        btn.setOnClickListener{
            Toast.makeText(this, "This is toast!", Toast.LENGTH_SHORT).show() // (activity, message, time)
        }
    }
}