JPopupMenu's MenuItems not responding to changes... why?

Question

I noticed that once my JPopupMenu becomes visible for the first time, its MenuItems do not reflect changes made to them for the next visibility. Here is the code;

private static void addListener(final JPopupMenu popup, final String someLetter)
{
    popup.addPopupMenuListener(new PopupMenuListener(){            
        @Override
        public void popupMenuWillBecomeVisible(PopupMenuEvent evt)
        {
            JMenuItem menuItem3 = (JMenuItem)popup.getComponent(3); 
            String[] letters = {"A", "B", "C", "D"};
            ArrayList<String> lettersList = new ArrayList<String>();
            lettersList.addAll(Arrays.asList(letters));
            if(lettersList.contains(someLetter)){
                menuItem3.setEnabled(true);
            }
            else{
                menuItem3.setEnabled(false);
            }
        }
    });
}

Normally I would expect that the lines under popupMenuWillBecomeVisible will always execute whenever the popupMenu is getting popped-up. But to my surprise it only works on the first time and subsequently does not test for the condition specified to to either enable or disable menuItem3. Please let somebody kindly help a brother out!

Answer 1

This seems to work quite well for me. Check out the example below which displays 5 menu items and toggles their "enability" everytime you perform a right-click:

import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;

import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;

public class TestPopupMenu {

    private void initUI() {
        final JFrame frame = new JFrame(TestPopupMenu.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        final JPopupMenu popup = new JPopupMenu();
        final List<JMenuItem> items = new ArrayList<JMenuItem>();
        for (int i = 0; i < 5; i++) {
            JMenuItem item = new JMenuItem(new AbstractAction("Action " + (i + 1)) {

                @Override
                public void actionPerformed(ActionEvent e) {
                    JOptionPane.showMessageDialog(popup, getValue(NAME) + " has been clicked");
                }
            });
            item.setEnabled(i % 2 == 0);
            items.add(item);
            popup.add(item);
        }
        popup.addPopupMenuListener(new PopupMenuListener() {

            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                for (JMenuItem item : items) {
                    item.setEnabled(!item.isEnabled());
                }
            }

            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {

            }

            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {

            }
        });
        panel.setComponentPopupMenu(popup);
        frame.add(panel);
        frame.setSize(300, 200);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnsupportedLookAndFeelException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new TestPopupMenu().initUI();
            }
        });
    }
}