Clearing Buffered Canvas

Question

Hi,
I've searched in google, on this forum and on JavaRanch Big Moose Saloon for the answer to this question but as of yet I can't find an answer.
I'm attempting to clear a JPanel canvas. Repaint() simply doesn't work so I've tried this,
public void clearImage()
Rectangle d = canvas.getBounds();                               //get canvas dimension
BufferedImage bi = new BufferedImage(d.width, d.height, BufferedImage.TYPE_INT_RGB);  //create new buffered image of canvas
Graphics2D g = bi.createGraphics();  //get canvas objects
g.setColor(Color.white);  //set colour to white
g.drawRect(10, 160, 210, 70);   //draw rectangle over buffered image.
}Although the code compiles fine, when I run this method, nothing happens. There are no errors throw. Simply nothing happens. I've also attempted the following code;
public void clearImage()
g = jPanel1.getGraphics();
g.setColor(Color.white);
g.fillRect(10, 160, 210, 70);
}which although it does cover the canvas with a white rectangle, once I click in the rectangle again, it removes it, and shows what was previously drawn in it.
If i try g = canvas.getGraphics(); on the top line, nothing happens again.
Any step in the right direction or an explanation of why the top method wont work would be appreciated greatly.
Thanks
N

Answer 1

Thankyou very much for the replies, they have helped out in understanding why the methods won't work.
However, I am still stuck on this. I thought that g.drawImage(bi, 0, 0, this); would draw the buffered image, yet nothing happens again.
At this point I'm getting really confused with images and graphics g and buffered images.
Here is my code so you can see how wrong I am going....
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
public class DrawPad extends JFrame implements ActionListener {
   private OutputScreen canvas;
   private javax.swing.JTextField barcode;
   private javax.swing.JButton exit;
   private javax.swing.JButton clearBarcode;
   private javax.swing.JButton clearCanvas;
   private javax.swing.JLabel jLabel1;
   private javax.swing.JLabel jLabel2;
   private javax.swing.JLabel jLabel3;
   private javax.swing.JPanel jPanel1;
   private javax.swing.JButton save;
   public DrawPad() {
     jPanel1 = new javax.swing.JPanel();
        barcode = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        exit = new javax.swing.JButton();
     canvas = new OutputScreen(Color.black);
     clearCanvas = new javax.swing.JButton();
     clearCanvas.addActionListener(new java.awt.event.ActionListener()
        public void actionPerformed(java.awt.event.ActionEvent e)
            clearImage();
     clearBarcode = new javax.swing.JButton();
     clearBarcode.addActionListener(new java.awt.event.ActionListener()
        public void actionPerformed(java.awt.event.ActionEvent e)
             barcode.setText("");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
     jPanel1.setLayout(null);
     getContentPane().add(jPanel1);
     canvas.setLayout(null);
     canvas.setBackground(new java.awt.Color(255, 255, 255));
        canvas.setBorder(new javax.swing.border.LineBorder(new java.awt.Color(0, 0, 0)));
        jPanel1.add(canvas);
        canvas.setBounds(10, 160, 210, 70);
        jPanel1.add(barcode);
        barcode.setBounds(20, 70, 180, 50);
        jLabel1.setText("Scan Package");
        jPanel1.add(jLabel1);
        jLabel1.setBounds(20, 40, 180, 20);
        jLabel2.setText("Sign Here Please");
        jPanel1.add(jLabel2);
        jLabel2.setBounds(10, 140, 210, 20);
        save.setText("Save");
        jPanel1.add(save);
        save.setBounds(70, 240, 59, 25);
            exit.setIcon(new javax.swing.ImageIcon("windows\\start menu\\programs\\CrE-ME\\images\\redbutton.gif"));
        exit.setBorder(null);
        exit.setOpaque(false);
        jPanel1.add(exit);
        exit.setBounds(160, 10, 25, 25);
     clearBarcode.setText("Clear");
     jPanel1.add(clearBarcode);
     clearBarcode.setBounds(160, 120, 59, 25);
     clearCanvas.setText("Clear");
     jPanel1.add(clearCanvas);
     clearCanvas.setBounds(150, 230, 59, 25);
        //jPanel1.add(jLabel3);
        //jLabel3.setBounds(0, -5, 240, 280);
        getContentPane().add(jPanel1);
        jPanel1.setBounds(0, 0, 277, 344);
     addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                //exitForm(evt);
     this.setSize(new Dimension(240, 300));
     setVisible(true);
   ///////Method I am having problems with ////////////////////////////////////
   public void clearImage()
               Rectangle d = canvas.getBounds();                              
               BufferedImage bi = new BufferedImage(d.width, d.height, BufferedImage.TYPE_INT_RGB); 
               Graphics g = bi.createGraphics();
               g.setColor(Color.white); 
               g.drawRect(10, 160, 210, 70); 
               g.drawImage(bi, 0, 0, this);
     public void actionPerformed(ActionEvent e) {
      String s = e.getActionCommand();
   public static void main(String[] args) {
      new DrawPad().setVisible(true);
class OutputScreen extends JPanel {
   private BufferedImage buf;
   private Color currentColor;
   private Graphics2D g2;
   private Point lastPoint;
   public OutputScreen(Color initialColor) {
      setPreferredSize(new Dimension(240, 300));
      buf = new BufferedImage(240, 300, BufferedImage.TYPE_INT_RGB);
      g2 = buf.createGraphics();
      g2.setColor(Color.white);
      g2.fillRect(0, 0, 240, 300);
      g2.setColor(initialColor); 
      addMouseListener(new MouseAdapter()
public void mousePressed(MouseEvent e) {
            moveto(e.getPoint());  // Move to click position
            requestFocus();        // Take keyboard focus
      addMouseMotionListener(new MouseMotionAdapter() {
         public void mouseDragged(MouseEvent e) {
            Point p = e.getPoint();
            lineto(p); // Draw to mouse position
            moveto(p);
   public void setColor(Color c){
      g2.setColor(c);
   public void paintComponent(Graphics g){
      super.paintComponent(g);
      g.drawImage(buf, 0, 0,this);
   private void moveto(Point pt){
      lastPoint = pt;
   private void lineto(Point pt){
      g2.drawLine(lastPoint.x, lastPoint.y, pt.x, pt.y);
      repaint();
}Again thankyou for the replies you have already given, I really appreciate them.
Wishing everyone a Happy New Year!
N