kotlin-migrate-main-activity-class

public class MainActivity extends AppCompatActivity {

    List<String> doItList = new ArrayList<>();
    ArrayAdapter<String> adapter;
    ListView listView = null;
    TextView emptyView = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        listView = findViewById(R.id.listview);
        emptyView = findViewById(R.id.empty_view);

        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,
                doItList);
        listView.setAdapter(adapter);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showAddDoItItem();
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();

        refreshUI();
    }

    protected void refreshUI() {
        if (doItList.size() > 0) {
            listView.setVisibility(View.VISIBLE);
            emptyView.setVisibility(View.GONE);
            adapter.notifyDataSetChanged();
        } else {
            listView.setVisibility(View.GONE);
            emptyView.setVisibility(View.VISIBLE);
        }
    }

    protected void showAddDoItItem() {
        final EditText inputView = new EditText(this);
        inputView.setHint("Add Do Item Name");
        LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.WRAP_CONTENT
        );
        lp.setMargins(10, 10, 10, 10);
        inputView.setLayoutParams(lp);
        AlertDialog alertDialog = new AlertDialog.Builder(this)
                .setTitle("Do It")
                .setCancelable(true)
                .setView(inputView)
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        dialogInterface.dismiss();
                    }
                })
                .setPositiveButton("Add", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        doItList.add(inputView.getText().toString());
                        refreshUI();
                    }
                })
                .create();
        alertDialog.show();
    }
}