CardLayout布局的问题，请问怎么改？小菜求教

Question

首先，请看代码：//import ... 略去
public class VisualPanel_user {
JFrame jf = null ;
CardLayout card = null ;
public VisualPanel_user() {
JPanel jpN = new JPanel();
JPanel jpW = new JPanel();
JPanel jpC = new JPanel();
card = new CardLayout();

JLabel user_name = new JLabel("hello,"+Login_Cla.user_name);
    JLabel  title = new JLabel(" 欢迎进入系统 ");
    
    user_name.setFont(new java.awt.Font("华文行楷", 0, 30));
    title.setFont(new java.awt.Font("华文行楷", 0, 30));
    jpN.add(user_name);
    jpN.add(Box.createHorizontalStrut(100),"CENTER");
    jpN.add(title,"CENTER");
    jpN.add(Box.createHorizontalStrut(100),"CENTER");
    jpN.setBorder(new Border(){
public Insets getBorderInsets(Component c) {
return new Insets(10,10,10,10);
}
public boolean isBorderOpaque() {
return false;
}
public void paintBorder(Component c, Graphics g, int x, int y,
int width, int height) {
}});
    JScrollPane scroll=new JScrollPane();
    final JTree tree = new JTree();
    DefaultMutableTreeNode  root = new DefaultMutableTreeNode();
    DefaultMutableTreeNode  buy = new DefaultMutableTreeNode();
    DefaultMutableTreeNode  deposit = new DefaultMutableTreeNode();
    DefaultMutableTreeNode  money = new DefaultMutableTreeNode();
    DefaultMutableTreeNode  transfer = new DefaultMutableTreeNode();
    DefaultMutableTreeNode  withdraw = new DefaultMutableTreeNode();
    
    root.setUserObject("管理菜单");
    buy.setUserObject("购买商品");
    deposit.setUserObject("即时存款");
    money.setUserObject("资金查询");
    transfer.setUserObject("即时转账");
    withdraw.setUserObject("即时取款");
    
    root.add(buy);
    root.add(deposit);
    root.add(money);
    root.add(transfer);
    root.add(withdraw);
    
    DefaultTreeModel dtm = new DefaultTreeModel(root);
    
    tree.setModel(dtm);
    scroll.setViewportView(tree);
    jpW.add(scroll);//     final JPanel p_1 = new UserBuy_Cla();
//     final JPanel p_2 = new UserDeposit_Cla();
//     final JPanel p_3 = new UserMoney_Cla();
//     final JPanel p_4 = new UserTransfer_Cla();
//     final JPanel p_5 = new UserWithdraw_Cla();
    final JPanel p_1 = new JPanel();
    final JPanel p_2 = new JPanel();
    final JPanel p_3 = new JPanel();
    final JPanel p_4 = new JPanel();
    final JPanel p_5 = new JPanel();
    p_1.setBackground(Color.black);
    p_2.setBackground(Color.blue);
    p_3.setBackground(Color.cyan);
    p_4.setBackground(Color.DARK_GRAY);
    p_5.setBackground(Color.gray);
    jpC.setLayout(card);
    jpC.add(p_1,"buy");
    jpC.add(p_2,"deposit");
    jpC.add(p_3,"money");
    jpC.add(p_4,"transfer");
    jpC.add(p_5,"withdraw");
    
jf = new JFrame("在线销售系统");
jf.add(jpN,BorderLayout.NORTH);
jf.add(jpW,BorderLayout.WEST);
jf.add(jpC,BorderLayout.CENTER);
jf.pack();
jf.setVisible(true);

tree.addTreeSelectionListener(new TreeSelectionListener(){
public void valueChanged(TreeSelectionEvent e) {
DefaultMutableTreeNode select = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
if( select.toString().equals("购买商品") )
card.show(p_1,"buy");
else if( select.toString().equals("即时存款"))
card.show(p_2,"deposit");
else if( select.toString().equals("资金查询"))
card.show(p_3,"money");
else if( select.toString().equals("即时转账"))
card.show(p_4,"transfer");
else
card.show(p_5,"withdraw");
}});
}
public static void main(String[] args) {
new VisualPanel_user();
}
}问题：
点击【子节点】，弹出Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: wrong parent for CardLayout然后Eclipse显示出card.show(...)这里出错！
可是我的JPanel p_1到p_5装进jpC里面去了啊，jpC定义为CardLayout .问题在，但我不知道错在哪，也不会改？求指教！

Answer 1

你的 CardLayout.show(),用错了。第一个参数应该是 card 的 container
jpC, 而不应该是 card 自身。87行的 tree.addTreeSelectionListener
可更改为：
        final JPanel cards = jpC;
        tree.addTreeSelectionListener(new TreeSelectionListener(){
            public void valueChanged(TreeSelectionEvent e) {
                DefaultMutableTreeNode select = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
                if( select.toString().equals("购买商品") )
                    card.show(cards ,"buy");
                else if( select.toString().equals("即时存款"))
                    card.show(cards ,"deposit");
                else if( select.toString().equals("资金查询"))
                    card.show(cards ,"money");
                else if( select.toString().equals("即时转账"))
                    card.show(cards ,"transfer");
                else
                    card.show(cards ,"withdraw");
        }});

Answer 2

让类本身继承JFrame
取消使用frame就可以了

Answer 3

也谢谢你，提供这个思路！不过，想问你下，直接将类定义为extends JFrame和在类里面定义JFrame jf有区别么？

Answer 4

不用谢。修改后，我试了一下你的代码。写得不错，点击【子节点】的话，对应的 card 就会显示它的背景颜色。
大家互相学习！

Answer 5

一个是调用frame对象，一个是把自身看成frame对象

Answer 6

另外，两条小建议：// 建议1，加入这一行。（否则，关掉窗口后，你的 App 也不能停止）
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);final JPanel cards = jpC;
tree.addTreeSelectionListener(new TreeSelectionListener(){
  ......
  // 省略
  ......
});// 建议2，把这放到最后
jf.pack();
jf.setVisible(true);

Answer 7

作为java方面的初学者被人夸，受宠若惊！

Answer 8

谢谢，java小菜鸟明白了 ...