Background Painting of "Out of focus" tabbed Panel (JTabbedPane) ?

Question

Hi
I would like to add a on going Bar Graph to a JTabbedPane, this works fine if the specific Tab is in Focus, but when the tab is switched, Painting stops!
How can i ensure the painting continues in the background!
Here is an example which demo's the problem! Also, watch the standard out...
Any idea's how to solve this ?
import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
import javax.swing.JPanel;
import java.util.*;
public class TestPanel extends JPanel {
    // Define the height and width of the bars. Given by calling process.
    private int height [];
    private int width;
    // Define the starting point of the bar chart and base line.
    private int top = 5;
    private int base = 100 + top;
    private int middle = (base/2)+(top/2);
    private int baseOffset = 3;
    private int indent = 45;
    private int step = (base - top)/10;
    private int baseLen = 0;
    private int tpsArray[];
    private int maxValue;
    private int counter = 0;
    private int value;
    public TestPanel(String server, String file ) {
        tpsArray = new int[32768];
        JFrame f =  new JFrame();
        JTabbedPane t = new JTabbedPane();
        // Set the Content and Window layout
        f.setLayout( new BorderLayout() );
        t.add( panel(), "Tab A");
        t.add( new JLabel("I AM TAB B"), "Tab B");
        f.add( t, BorderLayout.CENTER);
        //f.setExtendedState( Frame.MAXIMIZED_BOTH );
        f.setSize(400,400);
        f.setVisible(true);
    public JPanel panel() {
        // Define the JPanel to hold the graphic
        JPanel panel = new JPanel( new BorderLayout());
        panel.setBackground( Color.white );
        AnnimationModel annimationModel = new AnnimationModel();
        AnimationView animationView = new AnimationView(annimationModel);
        panel.add(animationView, BorderLayout.CENTER);
        return panel;
    private class AnimationView extends JPanel {
        private Dimension d = new Dimension();
        AnimationView(AnnimationModel annimationModel) {
            // Save a reference to the model for use
            // when the view is updated
            annimationModel_ = annimationModel;
            // Listen for the events indicating that the model has changed
            annimationModel_.addObserver(new Observer() {
                public void update(Observable o, Object arg) {
                    // All we need to do is to get the view to repaint
                    AnimationView.this.repaint();
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = ( Graphics2D ) g;
            baseLen = getPanelWidth() - indent * 2 ;
            System.out.println("Painting Again.... Counter = " + counter  );
            int pos = ( indent + 6 );
            addOutLine(g2d);
            // Update the view based on the information in the model.
            g.setColor(Color.green);
            for ( int i=counter;i>0;i--) {
                if ( pos > ( baseLen + indent )  ) break;
                g.fill3DRect( pos, (base-tpsArray), 2, tpsArray[i], true );
pos = pos + 2;
tpsArray[counter] = value;
public int getPanelWidth() {
d.width = getWidth();
return d.width;
public void addOutLine(Graphics2D g2d) {
// Setup the percentage markings on left vertical bar
g2d.setColor( Color.GRAY );
g2d.setFont( new Font("Sanserif", Font.PLAIN, 10));
g2d.drawString( "0", (indent - 14), base + baseOffset );
// Display the last TPS rate
g2d.drawString( "" + maxValue, (indent - 20 ) , top+baseOffset );
// Display the last TPS rate
g2d.drawString( "(" + value + ")", 3, base + baseOffset );
// Draw vertical line from top of bar chart to base line
g2d.drawLine( indent, top, indent, base + baseOffset );
// Draw horizontal base line
g2d.drawLine( indent, base, indent+baseLen, base);
// Draw horizontal top tick mark
g2d.drawLine( (indent)-5, top, (indent)+5, top);
// Draw horizontal tick line at 50% or middle point
g2d.drawLine( (indent)-5, middle, (indent)+5, middle);
// Draw horizontal tick at bottom base line
g2d.drawLine( (indent)-5, base, (indent)+5, base);
// Draw the dotted lines across the bar chart.
g2d.setColor( new Color( 160,223,233));
float dashes[] = { 1 };
g2d.setStroke( new BasicStroke( 1, BasicStroke.JOIN_MITER, BasicStroke.JOIN_ROUND, 0, dashes, 0));
for (int i=base; i>=top ;i=i-step) {
g2d.drawLine( indent + 6, i, (indent+baseLen), i );
// The saved reference to the model
private AnnimationModel annimationModel_;
private class AnnimationModel extends Observable {
// private Shared sharedRef = new Shared();
AnnimationModel() {
Thread annimationThread = new Thread() {
public void run() {
while(true) {
try {
Thread.sleep(1000);
} catch ( Exception e ) {
value = 1 + (int) (Math.random() * 100 );
counter++;
// Notify the observers
setChanged();
notifyObservers();
annimationThread.start();
// Simple test main
static public void main(String[] args) {
TestPanel app = new TestPanel(null,null);
Thanks,
Rob

Answer 1

How can i ensure the painting continues in the background! Well, I don't think you force painting since Swing appears to be smart enough to not paint a component that isn't visible.
However, you should be able to do your painting on an offscreen image. So your offscreen image will be continually update. Then your paintComponent(...) method simply paints this offscreen image.
This posting should get your started using this approach:
http://forum.java.sun.com/thread.jspa?forumID=57&threadID=607073