Eventos da ChoiceGroup como POPUP (ComboBox)

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
 *
 * @author  wln1987
 * @version 0.1
 */
public class Midlet extends MIDlet implements CommandListener, ItemStateListener {
    
    private Form form = null;
    private ChoiceGroup choiceGroup = null;
    private Command exitCmd = new Command("Sair",Command.EXIT,0);
    
    public Midlet() {
        form = new Form("TESTE!");
        choiceGroup = new ChoiceGroup("", ChoiceGroup.POPUP);
        choiceGroup.append("Matriz", null);
        choiceGroup.append("Filial 1", null);
        choiceGroup.append("Filial 2", null);
        choiceGroup.append("Filial 3", null);
        form.append(choiceGroup);
        form.addCommand(exitCmd);
        form.setCommandListener(this);
        form.setItemStateListener(this);
   }
    
    
    public void startApp() {
        Display.getDisplay(this).setCurrent(form);
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }
    
    public void commandAction(Command command, Displayable displayable) {
        if(command == exitCmd) {
            destroyApp(true);
            notifyDestroyed();
        }
    }
    
    public void commandAction(Command command, Item item) {
    }
    
    public void itemStateChanged(Item item) {
        if(item == choiceGroup) {
            int i = choiceGroup.getSelectedIndex() ;
            paint();
            switch(i) {
                case 0:
                    form.append("MATRIZ SELECIONADA!");
                    break;
                case 1:
                    form.append("FILIAL 1 SELECIONADA!");
                    break;
                case 2:
                    form.append("FILIAL 2 SELECIONADA!");
                    break;
                case 3:
                    form.append("FILIAL 3 SELECIONADA!");
                    break;
                default:
                    break;
            }
        }
    }
    
    private void paint() {
        form.deleteAll();
        form.append(choiceGroup);
    }
}