How do I build a JMenu dynamically?

Question

I am trying to build a JMenu dynamically right when clicking in it (I'm only getting an empty menu), below is my code.

    final JMenu JMWindows = new JMenu("Opened Windows");                
    JMWindows.addActionListener(new ActionListener() {          
        @Override
        public void actionPerformed(ActionEvent e) {
            for(JInternalFrame ji : desktop.getAllFrames())
            {
                JMWindows.add(ji.getTitle());
            }               
        }
    });

I've realized that the actionperformed is never called, the JMenu is inside a JMenuBar. What could be the problem ?

For better help sooner, post an [SSCCE](http://sscce.org/). – Andrew Thompson Dec 11 '12 at 14:30 — Andrew Thompson, Dec 11 '12 at 14:30

David Kroukamp · Accepted Answer · 2012-12-11T16:59:29.597

You add ActionListener to JMenu this cannot be done for JMenu use MenuListener and set it via JMenu#addMenuListener(..)
Also you need to call revalidate() and repaint() on JMenu instance after adding/removing components from it or the changes will not be reflected (we could also call this on the containers instance i.e JMenuBar or JFrame, but we know only 1 specific JMenu will change so no need IMO).
Please watch your variable naming schemes JMWindow should be jmWindow/jMWindow variables always begin with no caps and the 1st letter of every new word thereafter gets capitalized (besides for constants and enums).

Here is an example using MenuListener:

enter image description here

import java.awt.*;
import java.awt.event.*;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;
import javax.swing.event.MenuEvent;
import javax.swing.event.MenuListener;

public class Test {

    private JDesktopPane jdpDesktop;
    private static int openFrameCount = 0;
    final JFrame frame = new JFrame("JInternalFrame Usage Demo");

    public Test() {

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // A specialized layered pane to be used with JInternalFrames
        jdpDesktop = new JDesktopPane() {
            @Override
            public Dimension getPreferredSize() {
                return new Dimension(500, 500);
            }
        };


        for (int i = 0; i < 3; i++) {
            createFrame(); // Create first window
        }

        frame.setContentPane(jdpDesktop);

        frame.setJMenuBar(createMenuBar());

        // Make dragging faster by setting drag mode to Outline
        jdpDesktop.putClientProperty("JDesktopPane.dragMode", "outline");

        frame.pack();
        frame.setVisible(true);
    }

    protected JMenuBar createMenuBar() {
        JMenuBar menuBar = new JMenuBar();
        JMenu menu = new JMenu("Frame");
        menu.setMnemonic(KeyEvent.VK_N);
        JMenuItem menuItem = new JMenuItem("New IFrame");
        menuItem.setMnemonic(KeyEvent.VK_N);
        menuItem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                createFrame();
            }
        });
        menu.add(menuItem);
        menuBar.add(menu);


        final JMenu jmWindows = new JMenu("Opened Windows");
        jmWindows.addMenuListener(new MenuListener() {
            @Override
            public void menuSelected(MenuEvent me) {
                jmWindows.removeAll();//remove previous opened window jmenuitems
                for (JInternalFrame ji : jdpDesktop.getAllFrames()) {
                    JMenuItem menuItem = new JMenuItem(ji.getTitle());
                    jmWindows.add(menuItem);
                }

                jmWindows.revalidate();
                jmWindows.repaint();
                jmWindows.doClick();

            }

            @Override
            public void menuDeselected(MenuEvent me) {
            }

            @Override
            public void menuCanceled(MenuEvent me) {
            }
        });
        menuBar.add(jmWindows);


        return menuBar;
    }

    protected void createFrame() {
        Test.MyInternalFrame frame = new Test.MyInternalFrame();
        frame.setVisible(true);
        // Every JInternalFrame must be added to content pane using JDesktopPane
        jdpDesktop.add(frame);
        try {
            frame.setSelected(true);
        } catch (java.beans.PropertyVetoException e) {
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Test();
            }
        });
    }

    class MyInternalFrame extends JInternalFrame {

        static final int xPosition = 30, yPosition = 30;

        public MyInternalFrame() {
            super("IFrame #" + (++openFrameCount), true, // resizable
                    true, // closable
                    true, // maximizable
                    true);// iconifiable
            setSize(300, 300);
            // Set the window's location.
            setLocation(xPosition * openFrameCount, yPosition
                    * openFrameCount);
        }
    }
}

@GuillaumePolet +1 true sorry about that cant remember where i saw that (updated post), and I was just warning OP as many people dont know standard variable naming schemes, never mind having to differentiate between variables and special variable naming schemes — David Kroukamp, Dec 11 '12 at 17:00

score 2 · Answer 2 · answered Dec 11 '12 at 13:33

2

You need to repaint and or validate your frame after adding or removing something. you can use the methods repaint() and validate() in your JFrame for this

answered Dec 11 '12 at 13:33

SomeJavaGuy

7,307
2
21
33

I tried both, repaint and validate inside the actionperformed but it is not working... I tried repainting and validating the container frame – HoNgOuRu Dec 11 '12 at 13:42

score 1 · Answer 3 · answered Dec 11 '12 at 13:48

You missed defining a JMenuItem.

    final JMenu JMWindows = new JMenu("Opened Windows");                
    JMWindows.addActionListener(new ActionListener() {          
        @Override
        public void actionPerformed(ActionEvent e) {
            for(JInternalFrame ji : desktop.getAllFrames())
            {
                JMenuItem menuItem = new JMenuItem(ji.getTitle());
                JMWindows.add(menuItem);
            }               
        }
    });

How do I build a JMenu dynamically?

3 Answers3

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