MainActivity.kt

class MainActivity : AppCompatActivity() {

   lateinit var binding: SampleBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = SampleBinding.inflate(layoutInflater, findViewById(android.R.id.content), true)
        supportFragmentManager.beginTransaction()
            .add(binding.frame.id, DemoFragment(), "Sample").commit()
    }
}