URGENT! Need help with scrolling on a JPanel!

Question

Hello Guys! I guess there has been many postings about this subject in the forum, but the postings I found there.... still couldn't solve my problem...
So, straight to the problem:
I am drawing some primitive graphic on a JPanel. This JPanel is then placed in a JScrollPane. When running the code, the scrollbars are showing and the graphic is painted nicely. But when I try to scroll to see the parts of the graphics not visible in the current scrollbarview, nothing else than some flickering is happening... No movement what so ever...
What on earth must I do to activate the scroll functionality on my JPanel??? Please Help!
And yes, I have tried implementing the 'Scrollable' interface... But it did not make any difference...
Code snippets:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import java.util.*;
public class FilterComp extends JPanel {//implements Scrollable {
  protected DefaultMutableTreeNode root;
  protected Image buffer;
  protected int lastW = 0;
  protected int origoX = 0;
  protected final StringBuffer sb = new StringBuffer();
//  protected int maxUnitIncrement = 1;
  protected JScrollPane scrollpane = new JScrollPane();
   *  Constructor for the FilterComp object
   *@param  scrollpane  Description of the Parameter
  public FilterComp(JScrollPane scrollpane) {
    super();
//    setPreferredSize(new Dimension(1000, 500));
    this.setBackground(Color.magenta);
//    setOpaque(false);
    setLayout(
      new BorderLayout() {
        public Dimension preferredLayoutSize(Container cont) {
          return new Dimension(1000, 600);
    this.scrollpane = scrollpane;
    scrollpane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    scrollpane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
    scrollpane.setPreferredSize( new Dimension( 500, 500 ) );
    scrollpane.getViewport().add( this, null );
//    scrollpane.getViewport().setScrollMode(JViewport.SIMPLE_SCROLL_MODE);
    repaint();
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    int w = getSize().width;
    if (w != lastW) {
      buffer = null;
    Graphics2D g2 = (Graphics2D) g;
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    if (root != null) {
      int h = getHeight(root);
      if (buffer == null) {
        buffer = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
        Graphics2D g3 = (Graphics2D) buffer.getGraphics();
        g3.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g3.setColor(Color.black);
        g3.setStroke(new BasicStroke(2));
        paint(g3, (w / 2) + origoX, 10, w / 2, root); 
      lastW = w;
      AffineTransform old = g2.getTransform();
      AffineTransform trans = new AffineTransform();
      trans.translate((w / 2) + origoX, (getHeight() - (h * 40)) / 2);
      g2.setTransform(trans);
      g2.drawImage(buffer, (-w / 2) + origoX, 0, null);
      g2.setTransform(old);
    updateUI();
   *  Description of the Method
   *@param  g  Description of the Parameter
  public void update(Graphics g) {
    // Call paint to reduce flickering
    paint(g);
   *  Description of the Method
   *@param  g2    Description of the Parameter
   *@param  x     Description of the Parameter
   *@param  y     Description of the Parameter
   *@param  w     Description of the Parameter
   *@param  node  Description of the Parameter
  private void paint(Graphics2D g2, int x, int y, int w, DefaultMutableTreeNode node) {
    if (node.getChildCount() == 2) {
      DefaultMutableTreeNode c1 = (DefaultMutableTreeNode) node.getChildAt(0);
      DefaultMutableTreeNode c2 = (DefaultMutableTreeNode) node.getChildAt(1);
      if (c1.getChildCount() == 0 && c2.getChildCount() == 0) {
        String s = c1.getUserObject().toString() + " " + node.getUserObject() + " " + c2.getUserObject();
        paint(g2, x, y, s);
      } else {
        g2.drawLine(x - (w / 2), y, x + (w / 2), y);
        Font f = g2.getFont();
        g2.setFont(new Font(f.getName(), Font.BOLD | Font.ITALIC, f.getSize() + 2));
        paint(g2, x, y, node.getUserObject().toString());
        g2.setFont(f);
        g2.drawLine(x - (w / 2), y, x - (w / 2), y + 40);
        g2.drawLine(x + (w / 2), y, x + (w / 2), y + 40);
        paint(g2, x - (w / 2), y + 40, w / 2, c1);
        paint(g2, x + (w / 2), y + 40, w / 2, c2);
    } else if (node.getChildCount() == 0) {
      paint(g2, x, y, node.getUserObject().toString());
   *  Description of the Method
   *@param  g2  Description of the Parameter
   *@param  x   Description of the Parameter
   *@param  y   Description of the Parameter
   *@param  s   Description of the Parameter
  private void paint(Graphics2D g2, int x, int y, String s) {
    y += 10;
    StringTokenizer st = new StringTokenizer(s, "\\", false);
    if (s.indexOf("'") != -1 && st.countTokens() > 1) {
      int sh = g2.getFontMetrics().getHeight();
      while (st.hasMoreTokens()) {
        String t = st.nextToken();
        if (st.hasMoreTokens()) {
          t += "/";
        int sw = g2.getFontMetrics().stringWidth(t);
        g2.drawString(t, x - (sw / 2), y);
        y += sh;
    } else {
      int sw = g2.getFontMetrics().stringWidth(s);
      g2.drawString(s, x - (sw / 2), y);
   *  Sets the root attribute of the FilterComp object
   *@param  root  The new root value
  public void setRoot(DefaultMutableTreeNode root) {
    this.root = root;
    buffer = null;
   *  Gets the root attribute of the FilterComp object
   *@return    The root value
  public DefaultMutableTreeNode getRoot() {
    return root;
   *  Gets the height attribute of the FilterComp object
   *@param  t  Description of the Parameter
   *@return    The height value
  private int getHeight(TreeNode t) {
    int h = 1;
    int c = t.getChildCount();
    if (c > 0) {
      if (c > 1) {
        h += Math.max(getHeight(t.getChildAt(0)), getHeight(t.getChildAt(1)));
      } else {
        h += getHeight(t.getChildAt(0));
    return h;
   *  Sets the x attribute of the FilterComp object
   *@param  x  The new x value
  public void setX(int x) {
    origoX = x;
   *  Gets the x attribute of the FilterComp object
   *@return    The x value
  public int getX() {
    return origoX;
   *  Gets the preferredScrollableViewportSize attribute of the FilterComp
   *  object
   *@return    The preferredScrollableViewportSize value
//  public Dimension getPreferredScrollableViewportSize() {
//    return getPreferredSize();
   *  Gets the scrollableBlockIncrement attribute of the FilterComp object
   *@param  r            Description of the Parameter
   *@param  orientation  Description of the Parameter
   *@param  direction    Description of the Parameter
   *@return              The scrollableBlockIncrement value
//  public int getScrollableBlockIncrement(Rectangle r, int orientation, int direction) {
//    return 10;
   *  Gets the scrollableTracksViewportHeight attribute of the FilterComp object
   *@return    The scrollableTracksViewportHeight value
//  public boolean getScrollableTracksViewportHeight() {
//    return false;
   *  Gets the scrollableTracksViewportWidth attribute of the FilterComp object
   *@return    The scrollableTracksViewportWidth value
//  public boolean getScrollableTracksViewportWidth() {
//    return false;
   *  Gets the scrollableUnitIncrement attribute of the FilterComp object
   *@param  r            Description of the Parameter
   *@param  orientation  Description of the Parameter
   *@param  direction    Description of the Parameter
   *@return              The scrollableUnitIncrement value
//  public int getScrollableUnitIncrement(Rectangle r, int orientation, int direction) {
//    return 10;
}

Answer 1

The Scrollable interface should be implemented by a JPanel set as the JScrollPane's viewport or scrolling may not function. Although it is said to be only necessary for tables, lists, and trees, without it I have never had success with images. Even the Java Swing Tutorial on scrolling images with JScrollPane uses the Scrollable interface.
I donot know what you are doing wrong here, but I use JScrollPane with a JPanel implementing Scrollable interface and it works very well scrolling images drawn into the JPanel.
You can scroll using other components, such as the JScrollBar or even by using a MouseListener/MouseMotionListener combination, but this is all done behind the scenes with the use of JScrollPane/Scrollable combination.
You could try this approach using an ImageIcon within a JLabel:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;
public class Test extends JFrame {
     BufferedImage bi;
     Graphics2D g_bi;
     public Test() {
          super("Scroll Test");
          makeImage();
          Container contentPane = getContentPane();
          MyView view = new MyView(new ImageIcon(bi));
          JScrollPane sp = new JScrollPane(view);
          contentPane.add(sp);
          setSize(200, 200);
          setVisible(true);
     private void makeImage() {
          bi = new BufferedImage(320, 240, BufferedImage.TYPE_INT_ARGB);
          g_bi = bi.createGraphics();
          g_bi.setColor(Color.white);
          g_bi.fillRect(0,0,320,240);
          g_bi.setColor(Color.black);
          g_bi.drawLine(0,0,320,240);
     public static void main(String args[]) {
          Test test = new Test();
class MyView extends JLabel {
     ImageIcon icon;
     public MyView(ImageIcon ii) {
          super(ii);
          icon = ii;
     public void paintComponent(Graphics g) {
          g.drawImage(icon.getImage(),0,0,this);
}Robert Templeton