E:\android\MyApplication\app\src\main\res\layout\activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#FF5722"
        android:textSize="30sp"
        android:textStyle="bold"
        android:textAllCaps="true"
        android:padding="10dp"
        android:layout_margin="10dp"
        android:gravity="center"
        android:layout_gravity="center"
        android:id="@+id/tv1"
        />
    <Switch
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Switch"
        android:textColor="#FF5722"
        android:textSize="30sp"
        android:textStyle="bold"
        android:textAllCaps="true"
        android:padding="10dp"
        android:layout_margin="10dp"
        android:gravity="center"
        android:layout_gravity="center"
        android:id="@+id/switch1"></Switch>

</LinearLayout>

E:\android\MyApplication\app\src\main\java\com\example\myapplication\MainActivity.kt

package com.example.myapplication
import android.os.Bundle
import android.widget.Switch
import androidx.activity.enableEdgeToEdge
import androidx.appcompat.app.AppCompatActivity
import android.widget.TextView


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)


        var tv: TextView?=null
        var swit: Switch?=null

        enableEdgeToEdge()
        setContentView(R.layout.activity_main)

        tv = findViewById(R.id.tv1)
        swit=findViewById(R.id.switch1)

        swit!!.setOnClickListener{
            if(swit!!.isChecked)
                tv!!.text=("SON")
            else
                tv!!.text=("SOFF")
        }

    }
}

Output: