Switch night mode kotlin

package com.example.nightmodebutton

import android.os.Bundle
import android.widget.CompoundButton
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate
import com.google.android.material.switchmaterial.SwitchMaterial

class MainActivity : AppCompatActivity() {

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

        // initialize variable
        val switchBtn: SwitchMaterial = findViewById(R.id.switchBtn)

        supportActionBar?.title = "LIGHT-NIGHT MODE SWITCH"

        // switch theme mode per user wishes
        // setting onCheckedListener on switch
        switchBtn.setOnCheckedChangeListener { buttonView, isChecked ->

            // checking if the switch is turned on
            if (isChecked) {

                // setting theme to night mode
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
                buttonView.text = "Night Mode"
            } else {

                // setting theme to light theme
                AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
                buttonView.text = "Light Mode"
            }
        }
    }
}