Jar 嵌入式资源 NullPointerException [英] Jar Embedded Resources NullPointerException
问题描述
我最初是从 Chillax 开始的，在临近截止日期遇到这么多问题之后，我又回到了我更熟悉的 IDE NetBeans，并将我的方法更改为更基本的Asteroid"类型游戏:
I originally started with Chillax, after Encountering so many problems so near to deadline, I went back to the IDE I am more familiar with, NetBeans, and I changed my approach to a more basic "Asteroid"-type game:
- NB 压缩文件:http://ge.tt/4T5tBFT/v/0?c
- 文本:git clone git://gist.github.com/4248746.git
- 嵌入?:
在 NetBeans 中我得到:
In NetBeans I get:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
at gayme.Craft.<init>(Craft.java:27)
at gayme.Board.<init>(Board.java:54)
at gayme.Gayme.<init>(Gayme.java:9)
at gayme.Gayme.main(Gayme.java:19)
Java Result: 1
来源:(工艺 26 - 34)
sources: (Craft 26 - 34)
public Craft() {
ImageIcon ii = new ImageIcon(this.getClass().getResource("craft.png"));
image = ii.getImage();
width = image.getWidth(null);
height = image.getHeight(null);
missiles = new ArrayList();
visible = true;
x = 40;
y = 60;}
(板 54)
craft = new Craft();
(同性恋 9)
add(new Board());
(同性恋 19)
new Gayme();
我有一些真正需要解决的问题，而我睡眠不足的大脑在每个问题上都遇到了问题.随时为您喜欢的任何游戏提供帮助.非常感谢各位！
I have issues that I really need resolved and my sleep deprived brain is coming up with a loss on each. Feel free to help out on whichever game you'd rather. Thanks so much guys!
推荐答案
有3种方法:
使用 Jar 文件和位于其中的资源时需要记住的一些事项:
A few things to remember about working with Jar files and resources located within:
JVM 区分大小写，因此文件和包名称区分大小写.即主类位于 mypackage 中，我们现在无法使用如下路径提取它:myPackAge
JVM is case sensitive thus file and package names are case sensitive. i.e Main class is located within mypackage we cannot now extract it with a path like: myPackAge
任何句点."位于包名内的应替换为/"
Any period '.' located within the package name should be replaced by '/'
如果名称以/"(u002f")开头，则资源的绝对名称是/"后面的名称部分.执行类时资源名称以/开头，资源在不同的包中.
If the name begins with a '/' ('u002f'), then the absolute name of the resource is the portion of the name following the '/'. Resource names begin with / when executing class and the resources are in different packages.
让我们使用我喜欢的 getResource(..) 方法进行测试，该方法将返回我们资源的 URL:
Lets put that to the test using my preferred method of getResource(..) which will return the URL of our resource:
我创建了一个包含 2 个包的项目:org.test 和 my.resources:
I create a project with 2 packages: org.test and my.resources:
如您所见，我的图像在 my.resources 中，而包含 main(..) 的 Main 类在 org.test 中>.
As you can see my image is in my.resources while the Main class which hold main(..) is in org.test.
Main.java:
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
public class Main {
public static final String RES_PATH = "/my/resources";//as you can see we add / to the begining of the name and replace all periods with /
public static final String FILENAME = "Test.jpg";//the case sensitive file name
/*
* This is our method which will use getResource to extarct a BufferedImage
*/
public BufferedImage extractImageWithResource(String name) throws Exception {
BufferedImage img = ImageIO.read(this.getClass().getResource(name));
if (img == null) {
throw new Exception("Input==null");
} else {
return img;
}
}
public static void main(String[] args) {
try {
BufferedImage img = new Main().extractImageWithResource(RES_PATH + "/" + FILENAME);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
如果您随意使用 RES_PATH 或 FILENAME 的名称而不对实际文件进行适当的更改，您将得到一个异常(只是向您展示我们必须多么小心带路径)
If you play around with the names of the RES_PATH or FILENAME without making appropriate changes to actual files you will get an exception (just shows yous how careful we must be with paths)
更新:
对于您的具体问题:
ImageIcon ii = new ImageIcon(this.getClass().getResource("craft.png"));
应该是:
ImageIcon ii = new ImageIcon(this.getClass().getResource("/resources/craft.png"));
Alien等类也需要修改.
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