package com.app;import java.awt.Button;
import java.awt.CardLayout;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;public class TestCardLayout extends WindowAdapter implements ActionListener{
private Frame frame;
private CardLayout cardLayout;

public void actionPerformed(ActionEvent e){
cardLayout.next(frame);
}

public void run(){
frame = new Frame("Test Card Layout");
frame.setSize(150,120);
frame.addWindowListener(this);
Button button1 = new Button("卡片1");
Button button2 = new Button("卡片2");
Button button3 = new Button("卡片3");
Panel panel1 = new Panel();
Panel panel2 = new Panel();
Panel panel3 = new Panel();
panel1.add(button1);
button1.addActionListener(this);
panel2.add(button2);
button2.addActionListener(this);
panel3.add(button3);
button3.addActionListener(this);
cardLayout = new CardLayout();
frame.add(panel1,"第1张");
frame.add(panel2,"第2张");
frame.add(panel3,"第3张");
frame.setVisible(true);

}

public void windowClosing(WindowEvent e){
System.exit(0);
}
public static void main(String[] args) {
TestCardLayout myCardLayout = new TestCardLayout();
myCardLayout.run(); }}没有语法错误,但是运行不了
Exception in thread "main" java.lang.IllegalArgumentException: cannot add to layout: unknown constraint: 第1张
at java.awt.BorderLayout.addLayoutComponent(BorderLayout.java:446)
at java.awt.BorderLayout.addLayoutComponent(BorderLayout.java:407)
at java.awt.Container.addImpl(Container.java:1068)
at java.awt.Container.add(Container.java:903)
at com.app.TestCardLayout.run(TestCardLayout.java:37)
at com.app.TestCardLayout.main(TestCardLayout.java:51)各位帮小弟看看是什么错误