kotlin-migrate-main-activity-kotlin-class

class MainActivity : AppCompatActivity() {
    internal var doItList: MutableList<String> = ArrayList()
    internal var adapter: ArrayAdapter<String>? = null
    internal var listView: ListView? = null
    internal var emptyView: TextView? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(layout.activity_main)
        val toolbar: Toolbar = findViewById(id.toolbar)
        setSupportActionBar(toolbar)
        listView = findViewById<ListView?>(id.listview)
        emptyView = findViewById<TextView?>(id.empty_view)
        adapter = ArrayAdapter(this, R.layout.simple_list_item_1,
                doItList)
        listView!!.adapter = adapter
        val fab: FloatingActionButton = findViewById(id.fab)
        fab.setOnClickListener { showAddDoItItem() }
    }

    override fun onResume() {
        super.onResume()
        refreshUI()
    }

    protected fun refreshUI() {
        if (doItList.size > 0) {
            listView!!.visibility = View.VISIBLE
            emptyView!!.visibility = View.GONE
            adapter!!.notifyDataSetChanged()
        } else {
            listView!!.visibility = View.GONE
            emptyView!!.visibility = View.VISIBLE
        }
    }

    protected fun showAddDoItItem() {
        val inputView = EditText(this)
        inputView.hint = "Add Do Item Name"
        val lp = LayoutParams(
                LayoutParams.MATCH_PARENT,
                LayoutParams.WRAP_CONTENT
        )
        lp.setMargins(10, 10, 10, 10)
        inputView.layoutParams = lp
        val alertDialog: AlertDialog = Builder(this)
                .setTitle("Do It")
                .setCancelable(true)
                .setView(inputView)
                .setNegativeButton("Cancel") { dialogInterface, i -> dialogInterface.dismiss() }
                .setPositiveButton("Add") { dialogInterface, i ->
                    doItList.add(inputView.text.toString())
                    refreshUI()
                }
                .create()
        alertDialog.show()
    }
}