MainActivity.kt

class MainActivity : AppCompatActivity() {

    ...
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        ...
        findViewById<FloatingActionButton>(R.id.floating_action_button).setOnClickListener {
            if (removedCurrencies.isNotEmpty()) {
                removedCurrencies.pop().let {
                    addRow(it)
                    addedCurrencies.add(it)
                }
            } else {
                Toast.makeText(this, R.string.no_more_items, Toast.LENGTH_SHORT).show()
            }
        }
    }
    ...
}