LazyAndDelegatesObservable.kt

class MainActivity : AppCompatActivity() {
    
    private val tvUsername: TextView by lazy { findViewById(R.id.tv_username) }
    private var text: String by Delegates.observable("Initial Value") { property, oldvalue, newValue ->
        tvUsername.text = newValue
    }
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        text = "Value has changed"
    }
    
}