Dear all,

I am a newbie in Java GUI...

My goal is that, I have a IPCam, and I want to write a Java GUI
application that refreshing the picture periodically, let say in a
simplier case - simply trigger by a button clicking.

The picture is a jpg image, let say "http://xxxx.com/imagegrab", it
will return the byte of JPG to u.

When I implement my work, I find the image cannot refresh.. It just
keep to be the very first image when I construct the GUI object.

Here is my code:

package testajay;
import java.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.lang.*;

public class IPCam {

    private int n;
    private String url_link = new
String("http://192.168.1.253/SnapshotJPEG?Resolution=320x240&Quality=Standard&Interval=30");
       private int temp;
    int counter = 0;
    public byte[] buffer = new byte[100000];

    public IPCam(String link) {
           this.download_URL(url_link, "./", link);
    }

    private byte[] downloadByteCodesFromURL(DataInputStream in) {

        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        while (true) {
            try {
                outStream.write(in.readByte());
            }
            catch (IOException e) {
                break;
            }
        }
        return outStream.toByteArray();
    }

    public void download_URL(String url_string, byte[] buf){
        try{
            URL u = new URL(url_string);
            DataInputStream data = new DataInputStream(u.openStream());

            // Download byte codes from URL Stream
            buf = downloadByteCodesFromURL(data);

            System.out.println("Downloaded! length = "+buf.length);
            temp = buf.length;

        }catch (Exception e){
            e.printStackTrace();
        }
    }

    public void download_URL(String url_string, String file_directory,
String filename){
        try{
            File saveFile = new File(file_directory, filename);
            FileOutputStream saveFileStream = new FileOutputStream(saveFile);

            URL u = new URL(url_string);
            DataInputStream data = new DataInputStream(u.openStream());

            // Download byte codes from URL Stream
            byte classBytes[] = downloadByteCodesFromURL(data);

            saveFileStream.write(classBytes, 0, classBytes.length);
            saveFileStream.flush();
            saveFileStream.close();

            System.out.println("Written! length = "+classBytes.length);

        }catch (Exception e){
            e.printStackTrace();
        }
    }

}

package testajay;

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

public class TestAjay extends JFrame{

   private JPanel picPanel;
   private JButton refresh;
   private Image image;
   JScrollPane jsp;

   private JLabel test_label;

   private int counter = 0;

   public TestAjay(){

       IPCam test = new IPCam("test.jpg");
       counter++;

       Container c = getContentPane();
       c.setLayout(new BorderLayout());
       refresh = new JButton("refresh");
       image = Toolkit.getDefaultToolkit().getImage("test.jpg");

       refresh.addActionListener(new ActionListener(){
           public void actionPerformed(ActionEvent e){
               if(e.getActionCommand() == "refresh"){

                   String baby;
                   if (counter%2==1){
                       baby = new String("test1.jpg");
                   }else{
                       baby = new String("test.jpg");
                   }
// I write this routine to test...
// everytime it will display intial test.jpg(the very first jpg I grab
when I construct the GUI), when I first click refresh, it will return
test1.jpg.... but from that on, I will only see test1.jpg no matter I
am requsting test.jpg or test1.jpg or not...
// I am very sure of that test1.jpg and test.jpg is changed and written
to a file correctly when I call IPCam test = new IPCam(baby);

                   IPCam test = new IPCam(baby);
                   ImageComponent ico = new ImageComponent(baby);
                   jsp.setViewportView(ico);
               }
           }
       });

       picPanel = new JPanel();
       picPanel.setLayout(new BorderLayout());
       ImageComponent ic = new ImageComponent(image);
       jsp = new JScrollPane(ic);
       picPanel.add(jsp, BorderLayout.CENTER);
       c.add(refresh,BorderLayout.NORTH);
       c.add(picPanel,BorderLayout.CENTER);
       setSize(400,400);
       setVisible(true);
   }

   class ImageComponent extends JLabel {
       Image img;
       ImageIcon ii;
       String imgFname;

       public ImageComponent(Image m){
           super();
           img = m;
           ii = new ImageIcon(img);
           setIcon(ii);
       }

       public ImageComponent(String fnam){
           super();
           imgFname = fnam;
           ii = new ImageIcon(imgFname);
           setIcon(ii);
       }
   }

   public static void main(String[] args){
       TestAjay app = new TestAjay();
       app.addWindowListener(new WindowAdapter(){
           public void windowClosing(WindowEvent e){
               System.exit(0);    
           }  
       });
   }
}