Question

我的Panel上有一个JComboBox。其中一个弹出菜单项是“更多”，当我点击它时，我会获取更多菜单项并将它们添加到现有列表中。在此之后，我希望保持弹出菜单打开，以便用户意识到已经获取了更多项目，但弹出窗口关闭。我正在使用的事件处理程序代码如下

public void actionPerformed(ActionEvent e)
    {
        if (e.getSource() == myCombo) {
            JComboBox selectedBox = (JComboBox) e.getSource();
            String item = (String) selectedBox.getSelectedItem();
            if (item.toLowerCase().equals("more")) {
                fetchItems(selectedBox);
            }
            selectedBox.showPopup();
            selectedBox.setPopupVisible(true);
        }
    }



private void fetchItems(JComboBox box)
    {
        box.removeAllItems();
        /* code to fetch items and store them in the Set<String> items */
        for (String s : items) {
            box.addItem(s);
        }
    }

我不明白为什么showPopup（）和setPopupVisible（）方法没有按预期运行。

Answer 1

在fetchItems方法中添加以下行

SwingUtilities.invokeLater(new Runnable(){

    public void run()
    {

       box.showPopup();
    }

}

如果你调用selectedBox.showPopup（）;在invokelater内部它也可以工作。

Answer 2

覆盖JCombobox setPopupVisible metod

public void setPopupVisible(boolean v) {
    if(v)
        super.setPopupVisible(v);
}

Answer 3

jComboBox1 = new javax.swing.JComboBox(){
@Override
public void setPopupVisible(boolean v) {
    super.setPopupVisible(true); //To change body of generated methods, choose Tools | Templates.
}

};

Answer 4

我找到了一些简单的解决方案，始终保持弹出窗口打开它可能对一些自定义的JComboBox有用，就像我在我的项目中那样，但是有点hacky。

public class MyComboBox extends JComboBox
{
    boolean keep_open_flag = false; //when that flag ==true, popup will stay open

    public MyComboBox(){
        keep_open_flag = true; //set that flag where you need
        setRenderer(new MyComboBoxRenderer()); //our spesial render
    }

    class MyComboBoxRenderer extends BasicComboBoxRenderer {

        public Component getListCellRendererComponent(JList list, Object value, 
            int index, boolean isSelected, boolean cellHasFocus) {

            if (index == -1){ //if popup hidden
                if (keep_open_flag) showPopup(); //show it again
            }
        }
    }
}

如何在填充JComboBox的弹出菜单时打开它？

4 个答案: