Jar Embedded Resources NullPointerException [英] Jar Embedded Resources NullPointerException
问题描述
我最初是从Chillax开始的，在遇到如此多的问题接近截止日期之后，我回到了我更熟悉的IDE，NetBeans，并且我改变了我的方法，以更基本的小行星型游戏：
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:
- NBs zip文件： http://ge.tt/4T5tBFT/v/0?c
- text：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;}
（Board 54）
craft = new Craft();
（Gayme 9）
add(new Board());
（Gayme 19）
new Gayme();
我有一些我真正需要解决的问题，我的睡眠不足的大脑每个人都会失去一个。随意帮助您选择相应的游戏。
非常感谢你们！
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：
- Class#getResourceAsStream(String name)
- Class#getResource(String name)
- ToolKit#createImage(URL url)
关于使用Jar文件和资源的一些注意事项：
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，我们现在无法使用以下路径提取它： 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
包名内的任何句号'。'应替换为'/'
Any period '.' located within the package name should be replaced by '/'
如果名称以'/'开头（'\ u002f' ），然后资源的绝对名称是'/'后面的名称部分。执行类时，资源名称以 / 开头，资源位于不同的包中。
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.
让我们使用我首选的 getResource（..）方法进行测试，它将返回我们资源的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:
正如您所见，我的图像是在 my.resources 中，而持有 main（..）的Main类位于 org.test 。
As you can see my image is in my.resources while the Main class which hold main(..) is in org.test.
Main.java：
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();
}
}
}
如果你使用 RES_PATH 或 FILENAME 的名称，而不对实际文件进行适当的更改，您将获得异常（只是显示我们对路径的谨慎程度）
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：
您的具体问题：
ImageIcon ii = new ImageIcon(this.getClass().getResource("craft.png"));
它应该是：
ImageIcon ii = new ImageIcon(this.getClass().getResource("/resources/craft.png"));
Alien 和其他类还需要改变。
The Alien and other classes also need to be changed.
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