import javax.swing.*;import java.awt.event.*;import java.awt.*;
import java.applet.*;import java.awt.CardLayout;
public class Sb_5_7 extends Applet implements ActionListener{
//卡布局
JLabel l1=new JLabel("one");
JLabel l2=new JLabel("two");
JButton b1=new JButton("向前");
JButton b2=new JButton("向后");
CardLayout card=new CardLayout();
BorderLayout bord=new BorderLayout();
JFrame f;
JPanel p1;JPanel p2;
public void init(){
f=new JFrame();
Container con=f.getContentPane();
con.setLayout(bord);
setSize(400,150);
setVisible(true);
JPanel p1=new JPanel();
p1.setLayout(card);
p1.add(l1);p1.add(l2);
JPanel p2=new JPanel();
b1.addActionListener(this);b2.addActionListener(this);
p2.add(b1);p2.add(b2);
con.add(p1,"Center");con.add(p2,"South");
}
public void actionPerformed(ActionEvent e){
if(e.getActionCommand().equals("向前")) card.last(p1);
else card.next(p1);
}
}
请问下大家，我这个程序可以运行，但为什么出现一个白板，我定义的东西，怎么都没显示，哪里错了，麻烦帮我改下，谢谢了
------解决方案--------------------
- Java code
import javax.swing.*;import java.awt.event.*;import java.awt.*;import java.applet.*;import java.awt.CardLayout;public class Sb_5_7 extends Applet implements ActionListener { // 卡布局 JLabel l1 = new JLabel("one"); JLabel l2 = new JLabel("two"); JButton b1 = new JButton("向前"); JButton b2 = new JButton("向后"); CardLayout card = new CardLayout(5,5); BorderLayout bord = new BorderLayout(); JFrame f; JPanel p1; JPanel p2; public void init() { f = new JFrame(); Container con = f.getContentPane(); con.setLayout(bord); setSize(400, 150); setVisible(true); p1 = new JPanel(); p1.setLayout(card); p1.add(l1,"a"); p1.add(l2,"b"); p2 = new JPanel(); b1.addActionListener(this); b2.addActionListener(this); p2.add(b1); p2.add(b2); con.add(p1, "Center"); con.add(p2, "South"); f.pack(); f.setVisible(true); } public void actionPerformed(ActionEvent e) { if (e.getActionCommand().equals("向前")) card.last(p1); else card.next(p1); }}