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Double-buffering problem

msulli1355 Posted: Sun Apr 18, 2004 5:31 am

Joined: 17 Apr 2004

Posts: 28

Double-buffering problem

I`m trying to write a game in Java. I primarily use Linux and for some
reason Java images in Linux flicker badly. I`m trying to find a way
around this so that my images don`t flicker. I`d like to use
double-buffering, but I can`t get it to work right with a Java
application. I`m trying to use it in a subclass of Canvas. I typed up
a test example:

import java.awt.*;

public class dbExample extends Canvas
{
Graphics offscreen;
Image image;

public dbExample()
{
image = createImage(500, 500);
offscreen = image.getGraphics();
}

public void paint(Graphics g)
{
offscreen.setColor(Color.cyan);
offscreen.fillRect(0, 0, 400, 400);

g.drawImage(image, 0, 0, this);
}

public static void main(String args[])
{
new dbExample();
}
}

It compiles just fine, but when I try to run it, I get this error:

Exception in thread "main" java.lang.NullPointerException
at dbExample.<init>(dbExample.java:11)
at dbExample.main(dbExample.java:24)

Line 11 is offscreen = image.getGraphics();

Line 24 is just my instantiation of a dbExample object. I want to use a
Canvas because the class I`m working on is just one part of the game and
I need something that can be added to a panel in the calling class.
I`ve gotten double-buffering to work with a JFrame, a JWindow, and an
applet. Can anyone help me???

-Michael Sullivan

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