kotlinでspinner

setOnItemSelectedListenerではないので注意

val spinner = findViewById<Spinner>(R.id.spinner)
spinner.onItemSelectedListener =
    object: AdapterView.OnItemSelectedListener {
        override fun onItemSelected(p0: AdapterView<*>?, p1: View?, p2: Int, p3: Long) {
            val i = p0 as Spinner
            Toast.makeText(this@MainActivity, i.selectedItem.toString(), Toast.LENGTH_SHORT).show()
        }
        override fun onNothingSelected(p0: AdapterView<*>?) {
        }
    }