Images not shown in Applet

Hi all!

I'm trying to write a simple site-navigation Applet using Java2D for painting the Applet.

What I've got so far worked (that is, images were displayed the way I expected) but now (and I can't figure out why) the Applet and the gradient paint in the background are shown, whereas the images are not. Debugging the Applet doesn't help, as the images are initialized using Applet parameters defined in the enclosing HTML page.

This is what I have written:

package navigationapplet;

import java.applet.Applet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Paint;
import java.awt.Toolkit;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * This class is created for a simple way to provide graphical site navigation
 * by means of an Applet that can be (ideally) customized by applet parameters
 * given in the web page's source code.
 *
 * The reason I preferred java.awt.Applet over javax.swing.JApplet is that quite
 * a couple of standard browsers don't seem to support JApplets in a satisfactory
 * way. The downside of this decision is that apparently I will have to do all the
 * serious gui stuff (such as painting the Applet or detecting mouseover events)
 * myself.
 *
 * @author Steffen Schmitt
 */
public class NavigationApplet extends Applet
{

private BufferedImage buffer;                            // the offscreen image buffer
    private Image[] images;                                  // the link images
    private Image[] rolloverImages;                          // the rollover images
    private Image activeLinkImage;                           // the active-link image (as yet unused)
    private Rectangle2D[] boxes;                             // the images' bounding boxes

@Override
    public void init ()
    {
        super.init ();
        setSize (960, 100);
        images = new Image[10];
        rolloverImages = new Image[images.length];
        boxes = new Rectangle2D[images.length];
        /* initialize images from Applet parameters */
        images[0] = getImage (getCodeBase (), getParameter ("image_0"));
        images[1] = getImage (getCodeBase (), getParameter ("image_1"));
        images[2] = getImage (getCodeBase (), getParameter ("image_2"));
        images[3] = getImage (getCodeBase (), getParameter ("image_3"));
        images[4] = getImage (getCodeBase (), getParameter ("image_4"));
        images[5] = null;
        images[6] = null;
        images[7] = null;
        images[8] = null;
        images[9] = null;
        
        /* initialize rollover images from Applet parameters*/
        rolloverImages[0] = getImage (getCodeBase (), getParameter ("rollover_0"));
        rolloverImages[1] = getImage (getCodeBase (), getParameter ("rollover_1"));
        rolloverImages[2] = getImage (getCodeBase (), getParameter ("rollover_2"));
        rolloverImages[3] = getImage (getCodeBase (), getParameter ("rollover_3"));
        rolloverImages[4] = getImage (getCodeBase (), getParameter ("rollover_4"));
        rolloverImages[5] = null;
        rolloverImages[6] = null;
        rolloverImages[7] = null;
        rolloverImages[8] = null;
        rolloverImages[9] = null;

/* for a maximum of 10 possible bounding boxes */
        for (int i = 0; i < 10; i++)
        {
            /* see if there is an image and a rollover image */
            if (images[i] != null && rolloverImages[i] != null)
            {
                /* then calculate bounding box and assign to array at the given index position */
                boxes[i] = new Rectangle2D.Float ((i * (images[i].getWidth (this) + 20) + 20),
                                                  getHeight () / 2 - images[i].getHeight (this) / 2,
                                                  images[i].getWidth (this),
                                                  images[i].getHeight (this));
            }

/* if there is no image or rollover image: */
            else
            {
                boxes[i] = null;
            }
        }
    }

@Override
    public void start ()
    {
        super.start ();
    }

@Override
    public void stop ()
    {
        super.stop ();
    }

@Override
    public void destroy ()
    {
        super.destroy ();
    }

@Override
    /* For double buffering purposes, this just calls paint(g). */
    public void update (Graphics g)
    {
        paint (g);
    }

@Override
    /* For double buffering purposes this just casts the Graphics object to a Graphics2D object
     * and draws a BufferedImage that is calculated using prepareImage()
     */
    public void paint (Graphics g)
    {
        super.paint (g);
        Graphics2D g2 = (Graphics2D) g;
        prepareImage ();
        g2.drawImage (buffer, 0, 0, null);
    }
    /* This calculates the offscreen image */
    public void prepareImage ()
    {
        /* initialize the BufferedImage */
        buffer = new BufferedImage (getWidth (), getHeight (), BufferedImage.TYPE_INT_RGB);
        Graphics g = buffer.getGraphics ();
        Graphics2D g2 = (Graphics2D) g;

/* fill whole Applet with gradient paint */
        Rectangle2D rect2 = new Rectangle2D.Float (0, 0, getWidth (), getHeight ());
        Paint p = new GradientPaint (getWidth () / 2, 
                                     0,
                                     new Color (50, 50, 50),
                                     getWidth () / 2,
                                     getHeight () / 2,
                                     new Color (75, 75, 75),
                                     true);

g2.setPaint (p);
        g2.fill (rect2);

/* This is where the images should be drawn: */
        for (int i = 0; i < 10; i++)
        {
            /* if image and rollover exist */
            if (images[i] != null && rolloverImages[i] != null)
            {

g2.drawImage (images[i],
                        (20 + i * (images[i].getWidth (this) + 20)),
                        getHeight () / 2 - images[i].getHeight (this) / 2,
                        this);
            }
        }
    }
}

The Applet's parameters are defined correctly in the enclosing HTML page (for better readability, I assigned a value of "null" in the param tag when no image fhile exists. This isn't used in the Applet):

<param name=rollover_0" value="images/Akelei_beschnitten_skaliert.JPG">
            <param name=rollover_1" value="images/Distel_beschnitten_skaliert.JPG">
            <param name=rollover_2" value="images/Gelbe_Blume_beschnitten_skaliert.JPG">
            <param name=rollover_3" value="images/Mohn_beschnitten_skaliert.JPG">
            <param name=rollover_4" value="images/Violette_Blume_beschnitten_skaliert.JPG">
            <param name=rollover_5" value="null">
            <param name=rollover_6" value="null">
            <param name=rollover_7" value="null">
            <param name=rollover_8" value="null">
            <param name=rollover_9" value="null">

<param name="url_0" value="http://www.steffen-schmitt.info">
            <param name="url_1" value="http://www.steffen-schmitt.info">
            <param name="url_2" value="http://www.steffen-schmitt.info">
            <param name="url_3" value="http://www.steffen-schmitt.info">
            <param name="url_4" value="http://www.steffen-schmitt.info">
            <param name="url_5" value="http://www.steffen-schmitt.info">
            <param name="url_6" value="http://www.steffen-schmitt.info">
            <param name="url_7" value="http://www.steffen-schmitt.info">
            <param name="url_8" value="http://www.steffen-schmitt.info">
            <param name="url_9" value="http://www.steffen-schmitt.info">
        </applet>

I'd be grateful for any suggestion, as I really can't figure out what went wrong.

Thanks in advance -

Steffen

Why are you using the "buffer" object for drawing? If you pass the "g2" object from the paint method into the prepareImage method, then you can use that for drawing directly.

Ulf Dittmer wrote:Why are you using the "buffer" object for drawing? If you pass the "g2" object from the paint method into the prepareImage method, then you can use that for drawing directly.

I thought I'd need the reference to a BufferedImage for double-buffered painting of the Applet. But why are th images not displayed? They were at first and then all of a sudden (do those things ever happen otherwise?) they weren't any more. That was about at the time when I was trying to calculate the images' bounding boxes. So, as far as I know, nothing of any structural importance had changed, but the images were gone ... strange!

I'll give it a try with passing in the g2 from the paint method, though. Thanks a lot for your recommendations!

Cheers -

Steffen