Swing Jcombobox将第一个元素设置为默认选中

【问题标题】：Swing Jcombobox set first element as default selectedSwing Jcombobox将第一个元素设置为默认选中
【发布时间】：2015-07-13 07:19:32
【问题描述】：

    String[] bookArray={"a","b","c"};
    JComboBox bookComboBox = new JComboBox(bookArray);
    bookComboBox.setSelectedIndex(0);
    bookComboBox.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            JComboBox cb= (JComboBox) e.getSource();
            bookNameSelected=(String) cb.getSelectedItem();
            System.out.println("book name selected:"+bookNameSelected);
            }
    });

如果用户没有选择任何值，下拉列表的第一个元素显示为默认值，但不会作为默认选择值传递。

【问题讨论】：

标签： java swing actionlistener jcombobox

【解决方案1】：

在ActionListener注册后移动bookComboBox.setSelectedIndex(0);，这允许ActionListener被触发并设置bookNameSelected

String[] bookArray = {"a", "b", "c"};
JComboBox bookComboBox = new JComboBox(bookArray);
bookComboBox.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        JComboBox cb = (JComboBox) e.getSource();
        bookNameSelected = (String) cb.getSelectedItem();
        System.out.println("book name selected:" + bookNameSelected);
    }
});
bookComboBox.setSelectedIndex(0);

【讨论】：