JComboBox não abre a lista de itens

Assuntos Gerais
#1

Boa tarde pessoal,

estava estudando uns exercícios com layouts e me deparei com uma coisa estranha, os 2 jcombobox que coloquei na tela não abre a lista de itens quando estão gerenciados no gridbaglayout. Alguem poderia me explicar onde estou errando?

[code]package swing_testes.testes;

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JTextField;

/**
*

  • @author Tebo Software - Shubacca

  • @date 16/05/2009
    */
    public class ReservasAereas extends JFrame {

    public ReservasAereas() {
    setTitle(“Reservas Aéreas”);
    setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
    addWindowListener(new WindowAdapter() {

         @Override
     public void windowClosing(WindowEvent e) {
         if (JOptionPane.showConfirmDialog(rootPane, "Fechar Janela?", "Atenção", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE) == JOptionPane.YES_OPTION) {
             System.exit(0);
         }
     }
 });

 //Dados da Reserva
 DefaultComboBoxModel dcbmDestinos = new DefaultComboBoxModel(new String[]{"Franca", "Ribeirão Preto", "São Paulo"});
 JPanel pnlReserva = new JPanel(new GridBagLayout());
 JLabel lblData = new JLabel("Data:");
 JTextField tfdData = new JTextField();
 JLabel lblDe = new JLabel("De:");
 final JComboBox cbxDe = new JComboBox();
 cbxDe.setModel(dcbmDestinos);
 JLabel lblAte = new JLabel("Até:");
 JComboBox cbxAte = new JComboBox();
 cbxAte.setModel(dcbmDestinos);
 JPanel pnlOpcoes = new JPanel(new GridLayout(3, 1));
 pnlOpcoes.setBorder(BorderFactory.createTitledBorder("Classe"));
 ButtonGroup bg = new ButtonGroup();
 JRadioButton rbtPrimeiraClasse = new JRadioButton("1ª Classe", true);
 JRadioButton rbtSegundaClasse = new JRadioButton("2ª Classe");
 JRadioButton rbtTerceiraClasse = new JRadioButton("3ª Classe");
 bg.add(rbtPrimeiraClasse);
 bg.add(rbtSegundaClasse);
 bg.add(rbtTerceiraClasse);
 pnlOpcoes.add(rbtPrimeiraClasse);
 pnlOpcoes.add(rbtSegundaClasse);
 pnlOpcoes.add(rbtTerceiraClasse);
 
 GridBagConstraints con = new GridBagConstraints();
 con.insets = new Insets(2, 2, 2, 2);

 pnlReserva.add(lblData, con);
 con.gridy = 1;
 pnlReserva.add(lblDe, con);
 con.gridy = 2;
 pnlReserva.add(lblAte, con);

 con.anchor = GridBagConstraints.CENTER;
 con.gridx = 1;
 con.gridy = 0;
 con.weightx = 1;
 con.fill = GridBagConstraints.HORIZONTAL;
 pnlReserva.add(tfdData, con);
 con.gridy = 1;
 pnlReserva.add(cbxDe, con);
 con.gridy = 2;
 pnlReserva.add(cbxAte, con);
 con.gridx = 2;
 con.gridy = 0;
 con.gridheight = 3;
 con.weightx = 0;
 con.fill = GridBagConstraints.NONE;
 pnlReserva.add(pnlOpcoes, con);

 JPanel pnlVoos = new JPanel(new BorderLayout());
 pnlVoos.setBorder(BorderFactory.createTitledBorder("Voos Disponíveis"));
 JList lstVoos = new JList(dcbmDestinos);
 JScrollPane srpVoos = new JScrollPane(lstVoos);
 pnlVoos.add(srpVoos, BorderLayout.CENTER);

 JPanel pnlBotoes = new JPanel();
 JButton btnBuscar = new JButton("Buscar");
 btnBuscar.addActionListener(new ActionListener() {

     public void actionPerformed(ActionEvent e) {
         cbxDe.showPopup();
         JOptionPane.showMessageDialog(rootPane, cbxDe.getModel().getSize());
     }
 });
 JButton btnComprar = new JButton("Comprar");
 JButton btnFechar = new JButton("Fechar");
 pnlBotoes.add(btnBuscar);
 pnlBotoes.add(btnComprar);
 pnlBotoes.add(btnFechar);

 getRootPane().setLayout(new BorderLayout());
 getRootPane().add(pnlReserva, BorderLayout.NORTH);
 getRootPane().add(pnlVoos, BorderLayout.CENTER);
 getRootPane().add(pnlBotoes, BorderLayout.SOUTH);
 pack();
 setLocation((Toolkit.getDefaultToolkit().getScreenSize().width - getWidth()) / 2 ,
         (Toolkit.getDefaultToolkit().getScreenSize().height - getHeight()) / 2);
 setVisible(true);

    }

    public static void main(String[] args) {

     new ReservasAereas();
 JFrame j = new JFrame("Teste");
 j.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
 j.add(new JComboBox(new String[]{"Teste1", "Teste2", "Teste3", "Teste4"}));
 j.pack();
 j.setVisible(true);

    }
    }
    [/code]

desde já agradçeo

#2