MainActivity.kt

class MainActivity : AppCompatActivity() {
var button: Button? = null
    var userNameField: EditText? = null
    var displayUserName: TextView? = null
override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        AndroidInjection.inject(this)
        setContentView(R.layout.activity_main)
        initViews()
    }
private fun initViews() {
        button = this.findViewById(R.id.set_user_name)
        userNameField = this.findViewById(R.id.name_field)
        displayUserName = this.findViewById(R.id.display_user_name)
this.button!!.setOnClickListener({
            displayUserName!!.text = "Hello ${userNameField!!.text}!"
        })
    }
}