How to use a JCombobox in JMenu?

I want to add a Combobox to my JMenu but its not working properly. When I click it the menu closes.

I tried to add a JMenuItem and a JPanel with the combobox to the menu but neither worked.

public class Combo extends JMenuBar{

    public Combo(){
        this.setBackground(Color.DARK_GRAY);
        this.setForeground(Color.WHITE);
        this.setBorder(null);
        this.add(createCombobox());
    }

    

    private JMenu createCombobox() {
        JMenu menu = new JMenu("test");
        JLabel box = new JLabel("Color");
        String[] colors = {"blue", "green", "yellow"};

        JComboBox<String> comboBox = new JComboBox<>(colors);

        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        panel.setBorder(new MatteBorder(0, 5, 0, 0, Color.DARK_GRAY));
        panel.setBackground(Color.DARK_GRAY);
        panel.add(box, BorderLayout.CENTER);
        panel.add(comboBox, BorderLayout.EAST);

        menu.add(panel);

        return menu;
    }
    
}

Solution

This idea seems like an anti pattern to me - it doesn't really make sense when you consider that you could use a sub menu to effectively get the same workflow in a more expected and user acceptable way.

(There's also a million or more technical issues why I wouldn't even try and use a JCombobox this way, but lets stick with the fact that there is a pre-existing acceptable UX workflow)

Take a look at How to Use Menus and How to Use Actions for some more details.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTextArea textArea = new JTextArea("A long time ago, in a galaxy far, far away...", 10, 30);

        public TestPane() {
            JMenuBar menuBar = new JMenuBar();
            JMenu menu = new JMenu("Text");
            menuBar.add(menu);

            JMenu color = new JMenu("Color");
            menu.add(color);

            ColorAction.Observer observer = new ColorAction.Observer() {
                @Override
                public void didSetColor(ColorAction action, Color color) {
                    textArea.setForeground(color);
                }
            };

            color.add(new ColorAction("Blue", Color.BLUE, observer));
            color.add(new ColorAction("Green", Color.GREEN, observer));
            color.add(new ColorAction("Yellow", Color.YELLOW, observer));

            setLayout(new BorderLayout());

            add(menuBar, BorderLayout.NORTH);
            add(new JScrollPane(textArea));
        }
    }

    public class ColorAction extends AbstractAction {
        private static Observer Observer;

        public interface Observer {
            public void didSetColor(ColorAction action, Color color);
        }

        private Color color;
        private Observer observer;

        public ColorAction(String text, Color color, Observer observer) {
            super(text);
            this.color = color;
            this.observer = observer;
        }

        public Color getColor() {
            return color;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            if (observer == null) {
                return;
            }
            observer.didSetColor(this, getColor());
        }
    }
}