请教一个题目，

ctrruby 2012-02-26 08:45:44

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

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爱摸鱼de老邪 2012-02-26

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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);

	}



}