Bug in code from Java Tutorial or is it just me?
I copied and pasted this code from the Sun Java Tutorial
http://java.sun.com/docs/books/tutorial/2d/basic2d/examples/ImageLabel.java
package sim;
/*
* Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
are met:
*
* -Redistribution of source code must retain the above copyright
notice, this
* list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright
notice,
* this list of conditions and the following disclaimer in the
documentation
* and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
contributors may
* be used to endorse or promote products derived from this software
without
* specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind.
ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
INCLUDING
* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE
* OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC.
("SUN")
* AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
LICENSEE
* AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR
ITS
* DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
ANY LOST
* REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
CONSEQUENTIAL,
* INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF
THE THEORY
* OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS
SOFTWARE,
* EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed, licensed or
intended
* for use in the design, construction, operation or maintenance of
any
* nuclear facility.
*/
import java.io.*;
import java.awt.*;
import java.awt.font.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
import javax.imageio.*;
public class ImageLabel extends Component {
/**
*
*/
public static void main(String args[]) {
JFrame frame = new JFrame("Image Label");
BufferedImage img = null;
try {
String imageFileName = "painting.gif";
img = ImageIO.read(new File(imageFileName));
} catch (IOException e) {
}
frame.add("Center", new ImageLabel(img, "Java 2D Graphics!"));
frame.pack(); // This is line 63 where the stack trace starts
frame.setVisible(true);
}
BufferedImage img;
String text;
Font font;
public ImageLabel(BufferedImage img, String text) {
this.img = img;
this.text = text;
font = new Font("Serif", Font.PLAIN, 36);
}
/* We want to size the component around the text. */
public Dimension getPreferredSize() {
FontMetrics metrics = img.getGraphics().getFontMetrics(font);
int width = metrics.stringWidth(text)*2;
int height = metrics.getHeight()*2;
return new Dimension(width, height);
}
public void paint(Graphics g) {
/* Draw the image stretched to exactly cover the size of the
* drawing area.
*/
Dimension size = getSize();
g.drawImage(img,
0, 0, size.width, size.height,
0, 0, img.getWidth(null), img.getHeight(null),
null);
/* Fill a rounded rectangle centered in the drawing area.
* Calculate the size of the rectangle from the size of the
text
*/
g.setFont(font);
FontRenderContext frc =
((Graphics2D)g).getFontRenderContext();
Rectangle2D bounds = font.getStringBounds(text, frc);
int wText = (int)bounds.getWidth();
int hText = (int)bounds.getHeight();
int rX = (size.width-wText)/2;
int rY = (size.height-hText)/2;
g.setColor(Color.yellow);
g.fillRoundRect(rX, rY, wText, hText, hText/2, hText/2);
/* Draw text positioned in the rectangle.
* Since the rectangle is sized based on the bounds of
* the String we can position it using those bounds.
*/
int xText = rX-(int)bounds.getX();
int yText = rY-(int)bounds.getY();
g.setColor(Color.black);
g.setFont(font);
g.drawString(text, xText, yText);
}
}
When I run it under Java 6 (jdk1.6.0) I get the following run-time
errors
Exception in thread "main" java.lang.NullPointerException
at sim.ImageLabel.getPreferredSize(ImageLabel.java:79)
at java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:702)
at java.awt.Container.preferredSize(Container.java:1576)
at java.awt.Container.getPreferredSize(Container.java:1561)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1609)
at javax.swing.JRootPane
$RootLayout.preferredLayoutSize(JRootPane.java:898)
at java.awt.Container.preferredSize(Container.java:1576)
at java.awt.Container.getPreferredSize(Container.java:1561)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1609)
at java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:702)
at java.awt.Container.preferredSize(Container.java:1576)
at java.awt.Container.getPreferredSize(Container.java:1561)
at java.awt.Window.pack(Window.java:663)
at sim.ImageLabel.main(ImageLabel.java:63)
I have no idea what could be causing this error so I'm hoping someone
can help me.
At first I *thought* the try..catch may be producing it, so I took
a .JPG image and put it in what I thought to be the correct place
(both at the root of the project and in the source directory) but to
no avail.
Thanks
J