I wrote a simple Swing program. When the click a button and select a jpg file, I want to show this picture in the JScollPanel, but it doesn't appear. The source is here:
private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                        
   if(evt.getSource() == this.jButton3) {
       JFileChooser chooser = new JFileChooser();
       chooser.setFileSelectionMode(JFileChooser.FILES_ONLY);
       FileNameExtensionFilter filter = new FileNameExtensionFilter("JPG & GIF Images", "jpg", "gif");
       chooser.setFileFilter(filter);
       int returnVal = chooser.showOpenDialog(this);
       if(returnVal == JFileChooser.APPROVE_OPTION) {
           this.jTextField4.setText(chooser.getSelectedFile().getAbsolutePath());
           try{
               this.jScrollPane2.add(new ImagePanel(1, chooser.getSelectedFile()));
           } catch(Exception e) {
               e.printStackTrace();
           }
           
       }
   }
}  

package auction.client;

import java.awt.Graphics;
import java.awt.Image;
import java.awt.geom.Point2D;
import java.io.File;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JPanel;

public class ImagePanel extends JPanel {
   //identifier
   private int ID;
   
   //on-screen position
   private Point2D.Double position;
   
   //imageIcon to paint on screen
   private ImageIcon imageIcon;
   
   //stores all ImagePanel children
   private Set panelChildren;
   
   //constructor initilizes position and image
   public ImagePanel(int identifier, String imageFileName) throws IOException {
       super(null);//specify null layou
       this.imageIcon = this.createImageIcon(imageFileName);
       
       this.init(identifier);
   }
   
   public ImagePanel(int identifier, byte[] imageData) {
       super(null);
       this.imageIcon = this.createImageIcon(imageData);
       
       this.init(identifier);
   }
   
   public ImagePanel(int identifier, ImageIcon icon) {
       super(null);
       this.imageIcon = icon;
       
       this.init(identifier);
   }
   
   public ImagePanel(int identifier, File iconFile) throws IOException {
       super(null);
       this.imageIcon = this.createImageIcon(iconFile);
       
       this.init(identifier);
   }
   
   private void init(int identifier) {
       setOpaque(false);//make transparent
       
       // set unique identifier
       ID = identifier;
       
       // set location
       position = new Point2D.Double(0, 0);
       setLocation(0,0);
       
       Image image = imageIcon.getImage();
       setSize(image.getWidth(this), image.getHeight(this));
       
       //create Set to store Panel childre
       panelChildren = new HashSet();
   }
   
   private ImageIcon createImageIcon(String fileName) {
       try {
           return new ImageIcon(ImageIO.read(new File(fileName)));
       } catch (IOException ex) {
           Logger.getLogger(ImagePanel.class.getName()).log(Level.SEVERE, null, ex);
       }
       return null;
   }
   
   private ImageIcon createImageIcon(byte[] imageData) {
       return new ImageIcon(imageData);
   }
   
   private ImageIcon createImageIcon(File file) throws IOException {
       return new ImageIcon(ImageIO.read(file));
   }
   
   //paint Panel to scree
   public void paintComponent(Graphics g) {
       super.paintComponent(g);
       
       //if image is ready, paint it to screen
       imageIcon.paintIcon(this, g, 0, 0);
   }
   
   public void add(ImagePanel panel, int index) {
       panelChildren.add(panel);
       super.add(panel, index);
   }
   
   public void remove(ImagePanel panel) {
       panelChildren.remove(panel);
       super.remove(panel);
   }
   
   public void setIcon(ImageIcon icon) {
       this.imageIcon = icon;
   }

   public ImageIcon getImageIcon() {
       return imageIcon;
   }

   public Point2D.Double getPosition() {
       return position;
   }

   public void setPosition(double x, double y) {
       this.position.setLocation(x, y);
       this.setLocation((int) x, (int) y);
   }

   public int getID() {
       return ID;
   }
   
   public Set getChildren() {
       return panelChildren;
   }
   
}

Who can help me?