Why won't my JMenuBar show up?

Question

I'm trying to make a GUI in java, but JMenuBar has been giving me a hard time for two days. Can someone please tell me why it isn't showing up?

import java.awt.*;
import javax.swing.*;
import javax.swing.JPanel;
import java.awt.event.*;
import java.awt.image.*;     
import java.io.*;
import java.util.Arrays;
import javax.imageio.ImageIO;

public class selectionFrame extends JFrame
 {
  Font name;
  Font title;

  public void setup() //can't use constructer because this isn't given a size until after it is constructed.
  { 
   //getContentPane().add(menuBar);
   setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   getContentPane().setLayout(new FlowLayout());
   //getContentPane().add(j);

   setJMenuBar(createMenuBar());
   //getContentPane().add(createMenuBar());  
  }

  public JMenuBar createMenuBar()
  {
   JMenuBar menuBar;
   JMenu m_file;
   JMenuItem mi_save;
   JMenuItem mi_load;

   JMenu m_edit;
   JMenuItem mi_tileHeight;
   JMenuItem mi_tileWidth;

   menuBar = new JMenuBar();
   m_file = new JMenu("File");
   m_edit = new JMenu("Edit");

   mi_save = new JMenuItem("Save file", KeyEvent.VK_S);
   mi_load = new JMenuItem("Load file", KeyEvent.VK_L);
   mi_tileHeight = new JMenuItem("Set tile height", KeyEvent.VK_H);
   mi_tileWidth = new JMenuItem("Set tile width", KeyEvent.VK_W);

   menuBar.add(m_file);
   m_file.add(mi_save);
   m_file.add(mi_load);

   menuBar.add(m_edit);
   m_edit.add(mi_tileHeight);
   m_edit.add(mi_tileWidth);

   return menuBar;
  }

  public static void main(String[] args) //run
  { 
   selectionFrame sel = new selectionFrame();
   sel.setLocationRelativeTo(null);
   sel.setSize((int) 400 + (sel.getInsets().left + sel.getInsets().right),(int) 400  + (sel.getInsets().top + sel.getInsets().bottom));

   sel.setVisible(true);
   sel.setTitle("Tiles/Meta");
   sel.setResizable(false);
   sel.setFocusable(true);
   sel.getContentPane().setSize(sel.getSize());
   sel.setLocation((int) sel.getX() - (sel.getWidth()/2),(int) sel.getY() -  (sel.getHeight()/2));
   sel.setup();
   sel.repaint();

   } 
 }

Answer 1

You have an awful lot of extra code there.

public class SelectionFrame extends JFrame
{
    Font name;
    Font title;

    public SelectionFrame()
    {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setJMenuBar(createMenuBar());
    }

    public JMenuBar createMenuBar()
    {
        JMenuBar menuBar;
        JMenu m_file;
        JMenuItem mi_save;
        JMenuItem mi_load;

        JMenu m_edit;
        JMenuItem mi_tileHeight;
        JMenuItem mi_tileWidth;

        menuBar = new JMenuBar();
        m_file = new JMenu("File");
        m_edit = new JMenu("Edit");

        mi_save = new JMenuItem("Save file", KeyEvent.VK_S);
        mi_load = new JMenuItem("Load file", KeyEvent.VK_L);
        mi_tileHeight = new JMenuItem("Set tile height",
        KeyEvent.VK_H);
        mi_tileWidth = new JMenuItem("Set tile width",
        KeyEvent.VK_W);

        menuBar.add(m_file);
        m_file.add(mi_save);
        m_file.add(mi_load);

        menuBar.add(m_edit);
        m_edit.add(mi_tileHeight);
        m_edit.add(mi_tileWidth);

        return menuBar;
    }

    public void main( String args[] )
    {

        SelectionFrame sel = new SelectionFrame();
        sel.setLocationRelativeTo(null);
        sel.setSize(400 + (sel.getInsets().left + > sel.getInsets().right), 400
        + (sel.getInsets().top + sel.getInsets().bottom));

        sel.setTitle("Tiles/Meta");
        sel.setResizable(false);
        sel.setFocusable(true);

        sel.getContentPane().add( new JLabel( "Content", SwingConstants.CENTER),
         BorderLayout.CENTER );
        sel.setLocation(sel.getX() - (sel.getWidth() / 2), sel.getY() - >             (sel.getHeight() / 2));
        sel.setVisible(true);

    }
}

That shows up with a menu bar and everything. if you add your content to the CENTER of the content pane (by default a border layout), the center automatically fills the whole content area, you don't have to resize anything.

This shows up as a window with a menu bar and everything works fine.

What platform are you doing this on? I'm on Vista, i get what i expect to see.

Answer 2

What Java version are you using? Your menu bar shows up fine in 1.6.0_10 on my system. Try wrapping the body of your main method in an invokeLater() call so that it runs on the correct thread, like so:

public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                selectionFrame sel = new selectionFrame();
                sel.setLocationRelativeTo(null);
                sel.setSize((int) 400 + (sel.getInsets().left + sel.getInsets().right), 
                            (int) 400 + (sel.getInsets().top + sel.getInsets().bottom));
                sel.setTitle("Tiles/Meta");
                sel.setResizable(false);
                sel.setFocusable(true);
                sel.getContentPane().setSize(sel.getSize());
                sel.setLocation((int) sel.getX() - (sel.getWidth() / 2),
                                (int) sel.getY() - (sel.getHeight() / 2));
                sel.setup();
                sel.setVisible(true); // Follow Kendrick's advice too.
            }
        });
    }