java - 对 JComboBox 使用 switch 语句

Question

我有一个 JComboBox 设置如下所示:

private String[] boxChoices = {"option 1", "option 2"};
JcomboBox box = new JCombobox(boxChoices);

box.addItemListener()
{ 
    public void itemStateChanged(ItemEvent event)  
    {
        int selection = box.getSelectedIndex();
        switch (selection)
        {
            case 0: JOptionPane.showMessageDialog(null, "you have selected option 1");
                break;
            case 1: JOptionPane.showMessageDialog(null, "you have selected option 2");
                break;
            default: break;
        }
    }
}

我的问题是，当我选择一个选项时，消息将显示两次而不是一次。例如，如果我选择选项 1，将出现以下内容:

you have selected option 1
you have selected option 1

发生这种情况的原因是什么？

Answer 1

除了@Blip的回答，你还可以使用actionListener。 JComboBox 的 actionEvent 仅在您更改选择时触发一次。

box.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            int selection = box.getSelectedIndex();
            switch (selection) {
                case 0:
                    JOptionPane.showMessageDialog(null, "you have selected option 1");
                    break;
                case 1:
                    JOptionPane.showMessageDialog(null, "you have selected option 2");
                    break;
                default:
                    break;
            }
        }
    });