java - 监听器在 Action 前运行

Question

我制作了一个自定义的 JComboBox。为此，我使用了包含 JCheckBoxMenuItem 的 JPopupMenu。但显然 PopupMenuListener popupMenuWillBecomeInvisible 在 JCheckBoxMenuItem 更改之前运行。任何想法如何解决？我不想向 JCheckBoxMenuItem 添加监听器。

public class ListenerTest  extends JFrame implements ActionListener, PopupMenuListener {

    private JPopupMenu menu;
    private List<JCheckBoxMenuItem> menuItems;

    private JCheckBoxMenuItem i1;
    private JCheckBoxMenuItem i2;
    private JCheckBoxMenuItem i3;

    public ListenerTest(){

        // Create button
        JButton b = new JButton("Click me!");
        b.addActionListener(this);

        // Create Popupmenu
        menu = new JPopupMenu();
        menu.addPopupMenuListener(this);

        // Add CheckBoxes to PopupMenu 
        menuItems = new LinkedList<JCheckBoxMenuItem>();
        i1 = new JCheckBoxMenuItem("1");
        i2 = new JCheckBoxMenuItem("2");
        i3 = new JCheckBoxMenuItem("3");
        menu.add(i1);
        menu.add(i2);
        menu.add(i3);

        this.add(b);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.pack();
        this.setVisible(true);
    }

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

    @Override
    public void actionPerformed(ActionEvent e) {
        // Show PopupMenu when button is clicked
        menu.show(this, 0, this.getHeight());
    }

    @Override
    public void popupMenuWillBecomeVisible(PopupMenuEvent e) {}

    @Override
    public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
        // Check which checkBoxes is checked when popup menu is closed(currently one step behind)
        System.out.println(i1.isSelected());
        System.out.println(i2.isSelected());
        System.out.println(i3.isSelected());
    }

    @Override
    public void popupMenuCanceled(PopupMenuEvent e) {}
}

Answer 1

一个“可能的”解决方案与杂乱无章，是使用您的 popupMenuWillBecomeInvisible(...) 但是将您的状态检查排队到 Swing 事件队列中，以便它稍后执行其操作，之后当前事件队列中的所有项目都已完成。但是，这不能保证有效。

@Override
public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {

  SwingUtilities.invokeLater(new Runnable() {
     public void run() {
        System.out.println(i1.isSelected());
        System.out.println(i2.isSelected());
        System.out.println(i3.isSelected());
     }
  });
}