Pourquoi mon JmenuBar ne montre pas

Question

Je travaille sur un simple GUI.

Je n'arrive pas à voir la raison pour laquelle mon JMenuBar n'apparaît pas. Qu'est-ce que je rate?

Voici le code ci-dessous.

myMenuBar = new JMenuBar(); 
    myFileMenu = new JMenu("File"); 
    myRegisterItem = new JMenuItem("Register"); 
    myMenuBar.add(myFileMenu); 
    myFileMenu.add(myRegisterItem); 
    setJMenuBar(myMenuBar); 

La classe complète:

import java.awt.BorderLayout; 
import java.awt.EventQueue; 
import java.awt.GridBagConstraints; 
import java.awt.GridBagLayout; 
import java.awt.Insets; 
import java.rmi.Naming; 
import javax.swing.JButton; 
import javax.swing.JComboBox; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JOptionPane; 
import javax.swing.JPanel; 
import javax.swing.JPasswordField; 
import javax.swing.JScrollPane; 
import javax.swing.JTextArea; 
import javax.swing.JTextField; 
import javax.swing.UIManager; 
import javax.swing.UnsupportedLookAndFeelException; 
import javax.swing.border.EmptyBorder; 
import javax.swing.JMenu; 
import javax.swing.JMenuBar; 
import javax.swing.JMenuItem; 


public class GUI extends JFrame{ 


private JTextArea recievedField; 
private JButton sendButton; 
private JTextField messageField; 
private JComboBox itemComboBox; 
private JButton connectButton; 
private JTextField userNameField; 
private JPasswordField passwordField; 
private JButton loginButton; 
private JMenuBar myMenuBar; 
private JMenu myFileMenu; 
private JMenuItem myRegisterItem; 


public static void main(String[] args) { 
    new GUI(); 
} 

public GUI() { 
    EventQueue.invokeLater(new Runnable() { 
     @Override 
     public void run() { 

       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (Exception e) { 
        e.printStackTrace(); 
       } 

      JFrame frame = new JFrame("GUI"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.setLayout(new BorderLayout()); 
      frame.add(new MainPane()); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 
     } 

    }); 
} 

public class MainPane extends JPanel { 

    public MainPane() { 


     myMenuBar = new JMenuBar(); 
     setJMenuBar(myMenuBar); 
     myFileMenu = new JMenu("File"); 
     myRegisterItem = new JMenuItem("Register"); 
     myMenuBar.add(myFileMenu); 
     myFileMenu.add(myRegisterItem); 


     setBorder(new EmptyBorder(4, 4, 4, 4)); 
     setLayout(new GridBagLayout()); 
     GridBagConstraints gbc = new GridBagConstraints(); 
     gbc.gridx = 0; 
     gbc.gridy = 0; 
     gbc.weightx = 1; 
     gbc.fill = GridBagConstraints.HORIZONTAL; 
     gbc.gridwidth = GridBagConstraints.REMAINDER; 
     add(new LoginPane(), gbc); 
     gbc.gridy++; 
     add(new ConnectPane(), gbc); 
     gbc.gridy++; 
     gbc.weighty = 1; 
     gbc.fill = GridBagConstraints.BOTH; 
     add(new JScrollPane(recievedField = new JTextArea(5, 20)), gbc); 

     gbc.gridwidth = 1; 

     messageField = new JTextField(10); 
     sendButton = new JButton("Send"); 

     gbc.gridy++; 
     gbc.weighty = 0; 
     gbc.fill = GridBagConstraints.HORIZONTAL; 
     add(messageField, gbc); 
     gbc.gridx++; 
     gbc.weightx = 0; 
     gbc.insets = new Insets(5,5,5,5); 
     add(sendButton, gbc);   



    } 

} 

public class ConnectPane extends JPanel { 

    public ConnectPane() { 

     itemComboBox = new JComboBox(); 
     itemComboBox.addItem("Select an Item"); 
     connectButton = new JButton("Connect"); 

     setLayout(new GridBagLayout()); 
     GridBagConstraints gbc = new GridBagConstraints(); 
     gbc.gridx = 0; 
     gbc.gridy = 0; 
     gbc.anchor = GridBagConstraints.WEST; 
     gbc.insets = new Insets(5,5,5,5); 
     add(itemComboBox, gbc); 

     gbc.gridx++; 
     gbc.weightx = 1; 
     gbc.insets = new Insets(5,5,5,5); 
     add(connectButton, gbc); 
    } 

} 

public class LoginPane extends JPanel { 

    public LoginPane() { 

     userNameField = new JTextField(10); 
     passwordField = new JPasswordField(10); 
     loginButton = new JButton("Login"); 

     setLayout(new GridBagLayout()); 
     GridBagConstraints gbc = new GridBagConstraints(); 
     gbc.gridx = 0; 
     gbc.gridy = 0; 
     gbc.anchor = GridBagConstraints.WEST; 
     gbc.insets = new Insets(5,5,5,5); 
     add(new JLabel("User name:"), gbc); 

     gbc.gridx++; 
     gbc.insets = new Insets(5,5,5,5); 
     add(userNameField, gbc); 

     gbc.gridx++; 
     gbc.insets = new Insets(5,5,5,5); 
     add(new JLabel("Password:"), gbc); 

     gbc.gridx++; 
     gbc.insets = new Insets(5,5,5,5); 
     add(passwordField, gbc); 

     gbc.gridx++; 
     gbc.weightx = 1; 
     add(loginButton, gbc); 

    } 

} 

Answer 1

Votre problème est vous appelez setJMenuBar sur JPanel exemple cela est faux, vous devriez appeler:

frame.setJMenuBar(myMenuBar); 

pas besoin aussi pour:

frame.setLayout(new BorderLayout()); 

en tant que JFramecontentPane mise en page par défaut est BorderLayout

-à-dire changer votre code:

  JFrame frame = new JFrame("GUI"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.add(new MainPane()); 
      frame.setJMenuBar(myMenuBar); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 

Aussi ne pas utiliser EventQueue plutôt SwingUtilities:

SwingUtilities.invokeLater(new Runnable() { 
     @Override 
     public void run() { 

      try { 
       UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 

      JFrame frame = new JFrame("GUI"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.add(new MainPane()); 
      frame.setJMenuBar(myMenuBar); 
      frame.pack(); 
      frame.setLocationRelativeTo(null); 
      frame.setVisible(true); 
     } 
    }); 

Ne pas oublier de commenter le setJmenuBar(..) dans votre classe MainPane:

public MainPane() { 
     myMenuBar = new JMenuBar(); 

     //notice no call to setJMenuBar 

     myFileMenu = new JMenu("File"); 
     myRegisterItem = new JMenuItem("Register"); 
     myMenuBar.add(myFileMenu); 

     ... 
    } 

Answer 2

Son parce que vous avez défini votre JMenuBar visible.

Ajoutez ceci à votre code

frame.setJMenuBar(myMenuBar); // This line to be added 
    frame.pack(); 
    frame.setLocationRelativeTo(null); 
    frame.setVisible(true);