Simple Toast in Kotlin

main.xml

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout 
						   
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal|center_vertical"
android:padding="8dp"        
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent">

<Button
android:id="@+id/b1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="SHOW A TOAST"
android:textSize="14sp"/>

</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>




MainActivity.kt 



package com.toast.kotlin //your package name

import androidx.appcompat.app.AppCompatActivity

import android.widget.Button

import android.widget.Toast

import android.os.Bundle

public class MainActivity : AppCompatActivity() {

private lateinit var b1 : Button

    override fun onCreate(savedInstanceState: Bundle?) {

         super.onCreate(savedInstanceState)

         setContentView(R.layout.activity_main)

		 b1 = findViewById(R.id.b1) as Button         
                 
             b1.setOnClickListener{

			 Toast.makeText(this,"Hello this is a toast",3000).show()

			 }

    }

}