Menu Problems

[Alan Frentz]

Hi, I am working on a simple menu and running into a bit of difficulty. I have the menu created and it works well except for one issue, I cannot get the greying out of options to work. Specifically, when I select EDIT / OPTIONS / READ ONLY it should grey out the save/saveas options but instead I get a null pointer exception error. Your advice would be much appreciated. Thanks
Now for the code......

//  FileName Menutest.java
//  Sample Menu

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class MenuTest extends JFrame {
   private Action saveAction;
private Action saveAsAction;
private JCheckBoxMenuItem readOnlyItem;

   // set up GUI
   public MenuTest()
   {
      super( "Menu Test" );
//**********************************
//*   file menu and menu items
//**********************************
      // set up File menu and its menu items
      JMenu fileMenu = new JMenu( "File" );
      // set up New menu item
      JMenuItem newItem = fileMenu.add(new TestAction( "New" ));
      // set up Open menu item
      JMenuItem openItem = fileMenu.add(new TestAction( "Open" ));
//  add seperator bar
fileMenu.addSeparator();
      // set up Save menu item
      JMenuItem saveItem = fileMenu.add(new TestAction( "Save" ));
      // set up Save As menu item
      JMenuItem saveAsItem = fileMenu.add(new TestAction( "Save As" ));
//  add seperator bar
fileMenu.addSeparator();
// set up Exit menu item
      JMenuItem exitItem = new JMenuItem( "Exit" );
      exitItem.setMnemonic( 'x' );
      fileMenu.add( exitItem );
      exitItem.addActionListener(
         new ActionListener() {  // anonymous inner class
            // terminate application when user clicks exitItem
            public void actionPerformed( ActionEvent event )
            {
               System.exit( 0 );
            }
         }  // end anonymous inner class
      ); // end call to addActionListener
//**********************************
//*   Edit menu and menu items
//**********************************

// set up the Edit menu
JMenu editMenu = new JMenu( "Edit" );
//JMenuItem editMenu = new JMenu( "Edit" );
      // set up Cut menu item
      Action cutAction = new TestAction("Cut");
      cutAction.putValue(Action.SMALL_ICON, new ImageIcon("cut.gif"));
      // set up Copy menu item
      Action copyAction = new TestAction("Copy");
      copyAction.putValue(Action.SMALL_ICON, new ImageIcon("copy.gif") );
      // set up Paste menu item
      Action pasteAction = new TestAction("Paste");
      pasteAction.putValue(Action.SMALL_ICON, new ImageIcon("paste.gif") );
editMenu.add(cutAction);
editMenu.add(copyAction);
editMenu.add(pasteAction);
      //  add seperator bar
editMenu.addSeparator();
// set up Options menu, and it submenus and items
JMenu optionsMenu = new JMenu("Options");
readOnlyItem = new JCheckBoxMenuItem("Read-only");
readOnlyItem.addActionListener(
new ActionListener()
{  //  anonymous inner class
public void actionPerformed( ActionEvent event)
{
  saveAction.setEnabled(!readOnlyItem.isSelected());
  saveAsAction.setEnabled(!readOnlyItem.isSelected());
 }
  }  // end anonymous inner class
); // end call to addActionListener
optionsMenu.add(readOnlyItem);
// add seperator bar
optionsMenu.addSeparator();

//  Work on Radio Buttons
ButtonGroup textGroup = new ButtonGroup();
JRadioButtonMenuItem insertItem = new JRadioButtonMenuItem("Insert");
insertItem.setSelected(true);
JRadioButtonMenuItem overTypeItem = new JRadioButtonMenuItem("Overtype");
textGroup.add(insertItem);
textGroup.add(overTypeItem);
optionsMenu.add(insertItem);
optionsMenu.add(overTypeItem);
editMenu.add(optionsMenu);
//**********************************
//*   Help menu and menu items
//**********************************
// set up the Help menu
JMenu helpMenu = new JMenu( "Help" );
helpMenu.setMnemonic( 'H' );

      // set up index menu item
      JMenuItem indexItem = helpMenu.add(new TestAction( "Index" ));
      indexItem.setMnemonic( 'I' );
      helpMenu.add( indexItem );
// set up About menu item
      JMenuItem aboutItem = new JMenuItem( "About" );
      aboutItem.setMnemonic( 'A' );
      helpMenu.add( aboutItem );
      aboutItem.addActionListener(
         new ActionListener() {  // anonymous inner class
            // display message dialog when user selects Open
            public void actionPerformed( ActionEvent event )
            {
               JOptionPane.showMessageDialog( MenuTest.this,
                  "This is MenuTest.java \nVersion 1.0 \nMarch 15, 2004",
                  "About", JOptionPane.PLAIN_MESSAGE );
            }
         }  // end anonymous inner class
      ); // end call to addActionListener

      // create menu bar and attach it to MenuTest window
      JMenuBar bar = new JMenuBar();
      setJMenuBar( bar );
      bar.add( fileMenu );
bar.add( editMenu );
bar.add( helpMenu );
      setSize( 500, 200 );
      setVisible( true );

   } // end constructor
   public static void main( String args[] )
   {
      MenuTest application = new MenuTest();
      application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
   }
   // inner class to handle action events from menu items
   private class ItemHandler implements ActionListener {
      // process color and font selections
      public void actionPerformed( ActionEvent event )
      {
       repaint();
      } // end method actionPerformed
   } // end class ItemHandler

   //  Prints to action name to System.out
  class TestAction extends AbstractAction
   {
public TestAction(String name) { super(name); }

      public void actionPerformed( ActionEvent event )
      {
         System.out.println(getValue(Action.NAME) + " selected." );
      }
   } // end class TestAction
} // end class MenuTest

[Carlos Failde]

I draw your attention to these lines of code.
private Action saveAction;
private Action saveAsAction;
....
// set up Save menu item
JMenuItem saveItem = fileMenu.add(new TestAction( "Save" ));
// set up Save As menu item
JMenuItem saveAsItem = fileMenu.add(new TestAction( "Save As" ));
...
saveAction.setEnabled(!readOnlyItem.isSelected());
saveAsAction.setEnabled(!readOnlyItem.isSelected());