更新JComboBox popupMenu

Question

我有一个在开始时只有一个值的JComboBox，并且有一个连接到它的MouseListener。当我单击JComboBox时，我会用一些新值填充它。但popupMenu的大小相当于第一次单击JComboBox时的一个元素的大小。第二次，所有值都将显示为正常。你知道如何让comboBox在更新其内容后直接更新其popupMenu吗？

示例程序：

public class ComboBoxUpdate extends JFrame implements MouseListener {

    private JComboBox<String> box;
    public ComboBoxUpdate(){
        // Init
        JPanel panel = new JPanel();
        box = new JComboBox<String>();
        box.addItem("from start");

        // Add listener
        Component[] comps = box.getComponents();
        for(int i = 0; i < comps.length; i++)
            comps[i].addMouseListener(this);

        panel.add(box);
        this.add(panel);
        this.pack();
        this.setVisible(true);
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        if(box.getItemCount() == 1){
            box.removeAllItems();
            box.addItem("item 1");
            box.addItem("item 2");
            box.addItem("item 3");
        }
    }

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

    @Override
    public void mousePressed(MouseEvent e) {}

    @Override
    public void mouseReleased(MouseEvent e) {}

    @Override
    public void mouseEntered(MouseEvent e) {}

    @Override
    public void mouseExited(MouseEvent e) {}
}

Answer 1

我认为这是更好的解决方案：

public class ComboBoxUpdate extends JFrame implements PopupMenuListener {

    private JComboBox box;

    public ComboBoxUpdate() {
        // Init
        JPanel panel = new JPanel();
        box = new JComboBox();
        box.addItem("from start");

        box.addPopupMenuListener(this);

        panel.add(box);
        this.add(panel);
        this.pack();
        this.setVisible(true);
    }

    @Override
    public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
        if (box.getItemCount() == 1) {
            box.removeAllItems();
            box.addItem("item 1");
            box.addItem("item 2");
            box.addItem("item 3");
        }
    }

    @Override
    public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
    }

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

Answer 2

我有一个在开始时只有一个值的JComboBox，并且有一个连接到它的MouseListener。当我单击JComboBox时，我会用一些新值填充它

1. Item(s) to JComboBox on runtime可以是add/remove/modify into XxxComboBoxModel only
2. use DefaultComboBoxModel in you only all Items
3. MutableComboBoxModel for add/remove/modify Item(s) on runtime

Answer 3

尝试使用mousePressed()或mouseReleased()事件而不是mouseClicked()事件。此外，您还必须使用repaint()才能使更改可见。

       @Override
        public void mousePressed(MouseEvent e) {
            System.out.println("Pressed");
             if(box.getItemCount() == 1){
                 box.removeAllItems();
                 box.addItem("item 1");
                 box.addItem("item 2");
                 box.addItem("item 3");
                 repaint();
             }
        }