VanillaActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var textView: TextView

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

        textView = findViewById(R.id.textView)

        update()
    }

    private fun update() {
        textView.text = "Text"
        textView.setTextColor(Color.RED)
        textView.textSize = 14.0f
    }
}