kotlinでspinner動的生成

fun createSpinner(){
    var list = ArrayList<String>()
    list.add("1")
    list.add("2")
    list.add("3")

    val adapter = ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, list)
    val spinner = findViewById<Spinner>(R.id.spinner)
    spinner.adapter = adapter
}
createSpinner()