尝试使用ImageIO.read（class.getResource（URL））加载图像，但getResource返回null [英] Trying to load image using ImageIO.read(class.getResource(URL)) but getResource is returning null

问题描述

我和我的好友一起制作2D游戏，我通过一些Youtube教程学到了很多基本的游戏开发概念。我正在学习的其中一件事是精灵（对于那些不知道的人，2D图像渲染到屏幕上）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 getResource（）由于某种原因返回 null 。

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 null for some reason.

我一直在调整路径，添加 /在它前面，删除/，放入user.dir属性以查看它是否需要整个路径，我仍然得到相同的错误。

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.

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;
}

欢迎任何和所有帮助。
我没有评论代码（当我到达我可以坐下来的地方并且对我已经完成的内容感到满意时，我通常这样做）但这是一个非常小的课程，所以我认为你们会是能够理解发生了什么。

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.

在项目的类路径中保存图像 IS 的文件夹。
我还包括错误：

The folder that holds the image IS in the class path of my project. I've also included the error:

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)

再次感谢！

推荐答案

这个问题基本上与ImageIO无关，但是而是如何类 / ClassLoader.getResource 或 getResourceAsStream 有效。

This problem is basically unrelated to ImageIO, but rather how Class/ClassLoader.getResource or getResourceAsStream works.

有关说明，请参阅此答案。

在任何情况下，获取资源的这些方式只能从类路径中读取（即用户.dir 在这里永远不会有帮助。）

In any case, these ways of obtaining a resource will only be able to read from classpath (ie. user.dir will never help here).

这应该有效：

ImageIO.read(getClass().getResource("/path/to/resource"));

其中路径相对于类路径的 root （由领先的/).

Where the path is relative to the root of the classpath (specified by the leading /).

如果你的资源不在类路径上，只需使用：

If your resources are not on the classpath, simply use:

ImageIO.read(new File("path/to/resource");

路径相对于您的应用程序从启动的目录。

Where the path is relative to the directory your application was launched from.

这篇关于尝试使用ImageIO.read（class.getResource（URL））加载图像，但getResource返回null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！