Panel doesn't repaint on time

Question

Dear Java Community--
my current task is to develop a splash screen that can display messages, so that the user can see what happens during start up time.
My solution is a JPanel with a background image and the text on it. I overwrote the panel's paintComponent(Graphics g) method and use the Graphics object to draw the image, and the text as well. I use Java version 4.1.2_07. So far so good. ;-)
During startup time I have a dialog to popup that requests information from the user. The Splash stays in the back. After the dialog disappeared, my Splash should show up again and display some more messages.
My problem:
The dialog disappears but the Splash is not repainted immediately. The dialog leaves a big white area at the position it crossed the Splash. Also, the messages I add to the Splash are not beeing displayed. By the time the Slpash is repainted again (five or six seconds later), my application is up and running. That means, some of the messages (that were posted between dialog.hide() and application.show()) coudn't be delivert to the user at all.
My Question:
Do you have any suggestion what I could do to speed up my Splash and make it to repaint itself on time?
Thank you so much in advance!!!
Best regards,
Patrick
PS: Here's a part of the code:
     * we attach this panel to the content pane of this component
     * and overwrite the panel's paint method to display image, version and messages
    protected JPanel createPanel() {
        JPanel aPanel = new JPanel() {
            public void paintComponent(Graphics g) {
                //be sure not to break something
                super.paintComponent(g);
                //draw image
                _drawImage(g, image);
                //draw version number
                _drawVersionNumber(g, getVersion());
                //draw messages
                _drawMessages(g, messages);
        //set the same size as the surrounding window
        aPanel.setSize(getSize());
        //enable double buffering
        aPanel.setDoubleBuffered(true);
        //set transparent
        aPanel.setOpaque(false);
        return aPanel;
     * draws the defined image
     * @param g
     * @param image
    private void _drawImage(Graphics g, Image image) {
        if (image != null) {
            g.drawImage(image, 0, 0, this);
     * draws the given string in the lower right corner of the frame
     * @param g
     * @param version
    private void _drawVersionNumber(Graphics g, String version) {
        //draw version number
        g.setColor(getVersionColor());
        g.setFont(getVersionFont());
        //calculate string width
        FontMetrics fm = getFontMetrics(getVersionFont());
        int width = fm.stringWidth(version);
        //define position where to start
        int x = getWidth() - width - getPadding();
        int y = getHeight() - getPadding();
        //draw string
        g.drawString(version, x, y);
     * draws a list of messages (message by message) into the frame
     * @param g
     * @param messages - list strings to draw
    private void _drawMessages(Graphics g, java.util.List messages) {
        //set font
        g.setFont(getMessageFont());
        //calculate string height
        FontMetrics fm = getFontMetrics(getMessageFont());
        int fontHeigth = fm.getHeight();
        //draw messages
        int positionOffset = messages.size() - 1;
        for (int i = 0; i < Math.min(messages.size(), getMessageAmount()); i++) {
            Object message = messages.get(i);
            if (message != null) {
                //set color for this message
                Color c = getMessageColor();
                int alpha = 255;
                if (positionOffset == 1) {
                    alpha = 100;
                } else if (positionOffset > 1) {
                    alpha = 50;
                g.setColor(new Color(c.getRed(), c.getGreen(), c.getBlue(), alpha));
                //define clip area for drawing
                int clipWidth = getWidth() / 2;
                g.setClip(0, 0, clipWidth, getHeight());
                //draw message
                g.drawString(message.toString(), getPadding(), getHeight() - getPadding() - fontHeigth * positionOffset);
                //message longer than clip area? draw "..." after cutting the message
                if (fm.stringWidth(message.toString()) > clipWidth) {
                    g.setClip(0, 0, getWidth(), getHeight());
                    g.drawString("...", clipWidth, getHeight() - getPadding() - fontHeigth * positionOffset);
                //reduce offset for next message
                positionOffset--;
    }

Answer 1

The short answer is to use another thread. Everything in Swing runs on the Event
Dispatch Thread so you must post your gui changes to the edt queue to get them
shown. The Swing trail in the tutorial has a lesson on using threads and includes
links to additional resources. Here's a demo that might give you some ideas.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Currency
    JTextArea textArea;
    public Currency()
        textArea = new JTextArea();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(textArea));
        f.setSize(200,200);
        f.setLocation(100,100);
        f.setVisible(true);
        getUserInput(f);
    private void getUserInput(Frame f)
        // show splash screen used to keep user apprised
        // of our ongoing background activities
        final JWindow w = createSplashScreen(f);
        String s = "background work required...";
        final JTextArea ta = new JTextArea(s + "\n");
        w.add(ta);
        // forward gui update to event dispatch thread
        SwingUtilities.invokeLater(new Runnable()
            public void run()
                w.setVisible(true);
        String[] options = {
            "option 1", "option 2", "option 2"
        // get user selection, this is modal
        final Object retVal = JOptionPane.showInputDialog(null,
                                          "select an option, press \"OK\"",
                                          "background work scheduler",
                                          JOptionPane.PLAIN_MESSAGE,
                                          null,
                                          options,
                                          options[0]);
        if(retVal == null)
            /* defensive action */;
        // forward to edt queue for real-time gui update
        SwingUtilities.invokeLater(new Runnable()
            public void run()
                ta.setText((String)retVal + " chosen,\n\n" +
                           "background work starting..." + "\n");
        // now we can start the background activity
        startBackgroundWork(w, (String)retVal);
    private void startBackgroundWork(final JWindow splash, final String s)
        new Thread(new Runnable()
            public void run()
                int taskLength = 8, count = 0;
                while(count++ < taskLength)
                    textArea.append("count = " + count + "\n");
                    // if you had a JProgressBar in splash window
                    // you could update it from here...
                    // note gui is responsive to user during this
                    try
                        Thread.sleep(1000);
                    catch(InterruptedException ie)
                        System.err.println("interrupt: " + ie.getMessage());
                splash.dispose();
                textArea.setText(s + " loaded,\n\tready to go" + "\n");
        }).start();
    private JWindow createSplashScreen(Frame f)
        JWindow splash = new JWindow(f);
        splash.setSize(200,200);
        splash.setLocation(325,100);
        return splash;
    public static void main(String[] args)
        new Currency();
}