java 尝试使用 ImageIO.read(class.getResource(URL)) 加载图像但 getResource 返回 null
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Trying to load image using ImageIO.read(class.getResource(URL)) but getResource is returning null
提问by user2466959
I've been making a 2D game with my buddy and I've been learning a lot about some basic game dev concepts through some Youtube tutorials. One of the things I was learning about is sprites (for those that don't know, 2D images to render to the screen) and how to use them in my game. I've been using ImageIO.read(this.class.getResource(pathToMySprite))but it seems that getResource()is returning nullfor some reason.
我一直在和我的伙伴一起制作 2D 游戏，并且通过一些 Youtube 教程学习了很多关于一些基本游戏开发概念的知识。我正在学习的一件事是精灵（对于那些不知道的人，要渲染到屏幕上的 2D 图像）以及如何在我的游戏中使用它们。我一直在使用，ImageIO.read(this.class.getResource(pathToMySprite))但似乎由于某种原因getResource()正在返回null。
I've been screwing around with the path a little, adding "/" in front of it, removing "/", putting the user.dir property to see if it needed the whole path, and I'm still getting the same error.
我一直在修改路径，在它前面添加“/”，删除“/”，放置 user.dir 属性以查看它是否需要整个路径，但我仍然遇到相同的错误.
TILE_TEXTURES(System.getProperty("user.dir") + "/textures/tile.png");
//ENTITY_TEXTURES("/textures/entity.png");
private BufferedImage img;
private SpriteSheet(String path) {
System.out.println(System.getProperty("user.dir"));
try {
//TODO: Fix this error, don't know what's wrong.
img = ImageIO.read(SpriteSheet.class.getResource(path)); // error here!!!
} catch (IOException e) {
e.printStackTrace();
}
}
public BufferedImage getImage() {
return img;
}
Any and all help is appreciated. I haven't been commenting the code (I usually do that when I get to place where I can sit back and be happy with what I've finished) but it's a pretty small class so I think you guys will be able to understand what's going on just fine.
任何和所有的帮助表示赞赏。我没有评论代码（当我到达可以坐下来对我完成的东西感到满意的地方时，我通常会这样做）但这是一个非常小的课程，所以我想你们将能够理解什么是一切顺利。
The folder that holds the image ISin the class path of my project. I've also included the error:
保存影像的文件夹IS在我的项目的类路径。我还包括错误：
Exception in thread "Thread-2" java.lang.ExceptionInInitializerError
at com.brickbattle.client.src.gui.Sprite.<clinit>(Sprite.java:7)
at com.brickbattle.client.src.objs.Tile.<init>(Tile.java:67)
at com.brickbattle.client.src.objs.Player.initPlayerNum(Player.java:19)
at com.brickbattle.client.src.util.BrickBattle.init(BrickBattle.java:114)
at com.brickbattle.client.src.util.BrickBattle.run(BrickBattle.java:85)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalArgumentException: input == null! //HERE IS ERROR
at javax.imageio.ImageIO.read(Unknown Source)
at com.brickbattle.client.src.gui.SpriteSheet.<init>(SpriteSheet.java:17)
at com.brickbattle.client.src.gui.SpriteSheet.<clinit>(SpriteSheet.java:8)
Thanks again!
再次感谢！
回答by haraldK
This problem is basically unrelated to ImageIO, but rather how Class/ClassLoader.getResourceor getResourceAsStreamworks.
这个问题基本上与 ImageIO 无关，而是与Class/ClassLoader.getResource或如何getResourceAsStream工作有关。
For an explanation, see this answer.
有关解释，请参阅此答案。
In any case, these ways of obtaining a resource will only be able to read from classpath(ie. user.dirwill never help here).
在任何情况下，这些获取资源的方式都只能从类路径中读取（即user.dir在这里永远不会有帮助）。
This should work:
这应该有效：
ImageIO.read(getClass().getResource("/path/to/resource"));
Where the path is relative to the rootof the classpath (specified by the leading /).
其中路径相对于类路径的根（由前导 / 指定）。
If your resources are not on the classpath, simply use:
如果您的资源不在类路径上，只需使用：
ImageIO.read(new File("path/to/resource");
Where the path is relative to the directory your application was launched from.
路径相对于您的应用程序启动的目录的位置。
