Problems diplaying image on double buffered Panel

Question

Hello, I made a very simple image visualizer using double buffer. I load the images using ImageIO.read(File file) and display the image on the Panel by drawing it first to a buffer Image using a buffer Graphics, and then painting the buffer Image on the Panel surface. The problem is: sometimes the images are not dislplayed completely, and repainting again by calling repaint() does not work, it`s only displayed correctly if I try to resize the window. When I do the resizeing the paint function is called by a function other then repaint(), update(Graphics g) and paintComponents(Graphics g), and, this time, the paint() display the image correctly.
What should I do to always display the entire image? I apreciate any help.
Thankyou. Gustavo Peixoto
The code:
import java.awt.Graphics;
import java.awt.Panel;
import java.awt.image.BufferedImage;
public abstract class BufferGraphicsPanel extends Panel {
     private Graphics bufferGraphics;
     private BufferedImage bufferImage;
     private int bufferWidth;
     private int bufferHeight;
     public BufferGraphicsPanel() {
     public void resetBuffer() {
          bufferWidth = getWidth();
          bufferHeight = getHeight();
          if (bufferGraphics != null) {
               bufferGraphics.dispose();
               bufferGraphics = null;
          if (bufferImage != null) {
               bufferImage.flush();
               bufferImage = null;
          System.gc();
          bufferImage = (BufferedImage) createImage(bufferWidth, bufferHeight);
          bufferGraphics = bufferImage.getGraphics();
     public void paint(Graphics g) {
          System.out.println("paint");
          if (bufferWidth != getWidth() || bufferHeight != getHeight()
                    || bufferImage == null || bufferGraphics == null) {
               resetBuffer();
          bufferGraphics.clearRect(0, 0, bufferWidth, bufferHeight);
          paintBuffer(bufferGraphics);
          g.drawImage(bufferImage, 0, 0, this);
     public void update(Graphics g) {
          System.out.println("update");
          paint(g);
     public void repaint(){
          System.out.println("repaint");
          super.repaint();
     public abstract void paintBuffer(Graphics bufg);
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class VisualisadorDeImagens extends BufferGraphicsPanel {
     BufferedImage image;
     Frame frame;
     String dirPath;
     String fileNames[];
     int x, y;
     int pos;
     public static void main(String[] args) {
          new VisualisadorDeImagens(
                    "C:\\Documents and Settings\\All Users\\Documents\\My Pictures\\Sample Pictures");
     public VisualisadorDeImagens(String dirPath) {
          this.dirPath = dirPath;
          fileNames = new File(dirPath).list();
          frame = new Frame();
          frame.setSize(400, 200);
          frame.add(this);
          frame.addKeyListener(new KeyAdapter() {
               public void keyPressed(KeyEvent e) {
                    if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                         visualisar();
                    super.keyPressed(e);
          frame.addWindowListener(new WindowAdapter() {
               public void windowClosing(WindowEvent e) {
                    super.windowClosing(e);
                    frame.dispose();
                    System.gc();
                    System.exit(0);
          pos = 1;
          frame.setVisible(true);
     public void visualisar() {
          if (loadImage(dirPath + "\\" + fileNames[pos - 1])) {
               frame.setSize(image.getWidth(), image.getHeight() + 30);
          } else {
               frame.setSize(400, 200);
          frame.setTitle(fileNames[pos - 1]);
          pos = (pos % fileNames.length) + 1;
          repaint();
     public void paintBuffer(Graphics bufg) {
          if (image != null) {
               x = (frame.getWidth() / 2) - (image.getWidth() / 2);
               y = (frame.getHeight() / 2) - (image.getHeight() / 2);
               bufg.drawImage(image, x, y, this);
          } else
               bufg.drawString("Imagem indispon�vel", 130, 100);
     public boolean loadImage(String path) {
          try {
               image = ImageIO.read(new File(path));
          } catch (IOException e) {
               e.printStackTrace();
          if (image != null)
               return true;
          return false;
}

Answer 1

Hi camickr, thanks for the tip, I understood the approach used, but it`s different of mine. I know that what I`m doing works, I think I`m missing something. Thankyou.
ps. here is the code formated correctly:
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class VisualisadorDeImagens extends BufferGraphicsPanel {
     BufferedImage image;
     Frame frame;
     String dirPath;
     String fileNames[];
     int x, y;
     int pos;
     public static void main(String[] args) {
          new VisualisadorDeImagens(
                    "C:\\Documents and Settings\\All Users\\Documents\\My Pictures\\Sample Pictures");
     public VisualisadorDeImagens(String dirPath) {
          this.dirPath = dirPath;
          fileNames = new File(dirPath).list();
          frame = new Frame();
          frame.setSize(400, 200);
          frame.add(this);
          frame.addKeyListener(new KeyAdapter() {
               public void keyPressed(KeyEvent e) {
                    if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                         visualisar();
                    super.keyPressed(e);
          frame.addWindowListener(new WindowAdapter() {
               public void windowClosing(WindowEvent e) {
                    super.windowClosing(e);
                    frame.dispose();
                    System.gc();
                    System.exit(0);
          pos = 1;
          frame.setVisible(true);
     public void visualisar() {
          if (loadImage(dirPath + "\\" + fileNames[pos - 1])) {
               frame.setSize(image.getWidth(), image.getHeight());
          } else {
               frame.setSize(400, 200);
          frame.setTitle(fileNames[pos - 1]);
          pos = (pos % fileNames.length) + 1;
          repaint();
     public void paintBuffer(Graphics bufg) {
          if (image != null) {
               x = (frame.getWidth() / 2) - (image.getWidth() / 2);
               y = (frame.getHeight() / 2) - (image.getHeight() / 2);
               bufg.drawImage(image, x, y, this);
          } else
               bufg.drawString("Imagem indispon�vel", 130, 100);
     public boolean loadImage(String path) {
          try {
               image = ImageIO.read(new File(path));
          } catch (IOException e) {
               e.printStackTrace();
          if (image != null)
               return true;
          return false;
import java.awt.Graphics;
import java.awt.Panel;
import java.awt.image.BufferedImage;
public abstract class BufferGraphicsPanel extends Panel {
     private Graphics bufferGraphics;
     private BufferedImage bufferImage;
     private int bufferWidth;
     private int bufferHeight;
     public BufferGraphicsPanel() {
     public void resetBuffer() {
          bufferWidth = getWidth();
          bufferHeight = getHeight();
          if (bufferGraphics != null) {
               bufferGraphics.dispose();
               bufferGraphics = null;
          if (bufferImage != null) {
               bufferImage.flush();
               bufferImage = null;
          System.gc();
          bufferImage = (BufferedImage) createImage(bufferWidth, bufferHeight);
          bufferGraphics = bufferImage.getGraphics();
     public void paint(Graphics g) {
          System.out.println("paint");
          if (bufferWidth != getWidth() || bufferHeight != getHeight()
                    || bufferImage == null || bufferGraphics == null) {
               resetBuffer();
          bufferGraphics.clearRect(0, 0, bufferWidth, bufferHeight);
          paintBuffer(bufferGraphics);
          g.drawImage(bufferImage, 0, 0, this);
     public void update(Graphics g) {
          System.out.println("update");
          paint(g);
     public void repaint(){
          System.out.println("repaint");
          super.repaint();
     public abstract void paintBuffer(Graphics bufg);
}