为什么不能下一张
我想在application里实现随机验证码.不过不知道为什么不能下一张.
代码如下:

import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import javax.imageio.*;
import java.util.*;

public class RandomNumberPanel extends JPanel{
private String strRand;
private JLabel jlabel;

public RandomNumberPanel(){
jlabel=new JLabel();
this.add(jlabel);
getRandomImage();
}

private Color getRandomColor(int fc,int bc){
Random ra=new Random();
if(fc> 255) fc=255;
if(bc> 255) bc=255;

int r=fc+ra.nextInt(bc-fc);
int g=fc+ra.nextInt(bc-fc);
int b=fc+ra.nextInt(bc-fc);

return new Color(r,g,b);
}

public void nextImage(){
getRandomImage();
}

private void getRandomImage(){
int width=50;
int height=20;
try{
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics g=image.getGraphics();

Random r=new Random();

g.setColor(getRandomColor(200,250));
g.fillRect(0,0,width,height);
g.setFont(new Font( "Times New Roman ",Font.PLAIN,18));

g.setColor(getRandomColor(160,200));

for(int i=0;i <160;i++){
int x=r.nextInt(width);
int y=r.nextInt(height);
int x1=r.nextInt(12);
int y1=r.nextInt(12);

g.drawLine(x,y,x+x1,y+y1);
}

String sRand= " ";
for(int i=0;i <4;i++){
String s=String.valueOf(r.nextInt(10));
sRand+=s;
g.setColor(new Color(20+r.nextInt(110),20+r.nextInt(110),20+r.nextInt(110)));
g.drawString(s,13*i+6,16);
}

strRand=sRand;

g.dispose();

ImageIO.write(image, "JPEG ",new FileOutputStream( "tmp.jpg "));

jlabel.setIcon(new ImageIcon( "tmp.jpg "));
}catch(Exception e){
e.printStackTrace();
}

//this.remove(jlabel);
//this.add(jlabel);
SwingUtilities.updateComponentTreeUI(this);
}

public String getRandomString(){
return this.strRand;
}
}


import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MyDemo extends JFrame implements ActionListener{

private RandomNumberPanel rnp;
private JButton jb;

public MyDemo(){
rnp=new RandomNumberPanel();
jb=new JButton( "next ");
jb.addActionListener(this);
this.getContentPane().setLayout(new FlowLayout());
this.getContentPane().add(rnp);
this.getContentPane().add(jb);

pack();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}

public void actionPerformed(ActionEvent e){
rnp.nextImage();
SwingUtilities.updateComponentTreeUI(rnp);
}

public static void main(String[] args){
new MyDemo();
}
}

[解决办法]
LZ 把你的题意说明白！
[解决办法]
为了找这个原因至少花了1个小时,不过最终还是找到哪里有问题了,好高兴哦:

把jlabel.setIcon(new ImageIcon( "tmp.jpg "));
改成
jlabel.setIcon(new ImageIcon(image));