应用程序中的Java小程序

Question

I've written a Snake clone in the process of learning how to program in Java. It is an applet that uses images (loaded in the init() method using getImage(getDocumentBase(), "gfx/image.png");

When I run the applet in my IDE (Eclipse) it runs fine and all the images are shown.

My goal however is to create an executable jar file that I can pass around easier than an applet. So I created a new class and used a JPanel to host my applet. Now the problem is that getDocumentBase() always returns null, resulting in the images not being found on the filesystem, resulting in an empty screen.

I know the game runs cause I can navigate all the menus and see all the text that is printed. It's just the images that aren't loaded.

Is there any way around this? Should I load my images another way?

Thanks

Answer 1

You can load resources from within you jar-file by using the getResource() method from Class . On DevX there's a nice tutorial showing you how to do that for applets and applications:

http://www.devx.com/tips/Tip/5697

There is also an article from Oracle describing how to access resources in a location-independent manner:

http://download.oracle.com/javase/1.4.2/docs/guide/resources/resources.html

Basically you're accessing an image like this:

URL myurl = this.getClass().getResource("/myimage.gif");
Toolkit tk = this.getToolkit();
img = tk.getImage(myurl);

Answer 2

Load your image like this instead:

public void init() {
    URL url = getClass().getResource("/gfx/image.png");
    Image image = getImage(url);
}

Then add your gfx/image.png file to your jar and keep the path. Note that jar files are just zip files.