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

我一直在和我的好友一起制作 2D 游戏，并且通过一些 Youtube 教程学到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 getResource() 正在为 null 返回某种原因.

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，我仍然得到同样的错误.

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;
}

感谢任何和所有帮助.我没有评论代码(当我到达可以坐下来对我完成的事情感到满意的地方时，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.

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.

在我的项目的类路径中保存图像的文件夹IS.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

这个问题基本上和ImageIO无关，而是Class/ClassLoader.getResource或者getResourceAsStream 有效.

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

有关解释，请参阅此答案.

无论如何，这些获取资源的方式只能从类路径中读取(即user.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"));

其中路径是相对于类路径的根(由前导/指定).

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

如果您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");

路径相对于启动应用程序的目录.

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！