如何在JComboBox中显示自定义PopupMenu

import javax.swing.*;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;

public class CustomPopupMenuExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Custom PopupMenu Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        // 创建一个JComboBox对象
        JComboBox<String> comboBox = new JComboBox<>();
        comboBox.addItem("Option 1");
        comboBox.addItem("Option 2");
        comboBox.addItem("Option 3");
        
        // 创建一个JPopupMenu对象
        JPopupMenu popupMenu = new JPopupMenu();
        
        // 添加PopupMenuListener监听器
        comboBox.addPopupMenuListener(new PopupMenuListener() {
            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                // 获取选择项
                String selectedItem = (String) comboBox.getSelectedItem();
                
                // 根据选择项动态生成菜单项
                JMenuItem menuItem1 = new JMenuItem(selectedItem + " - Action 1");
                JMenuItem menuItem2 = new JMenuItem(selectedItem + " - Action 2");
                
                // 清空JPopupMenu中的菜单项
                popupMenu.removeAll();
                
                // 将菜单项添加到JPopupMenu中
                popupMenu.add(menuItem1);
                popupMenu.add(menuItem2);
            }
            
            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
                // Do nothing
            }
            
            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {
                // Do nothing
            }
        });
        
        // 将JComboBox设置为自定义的弹出菜单
        comboBox.setComponentPopupMenu(popupMenu);
        
        frame.add(comboBox);
        frame.setSize(300, 200);
        frame.setVisible(true);
    }
}