我在jar中尝试加载图像,但是getResourceAsStream()始终返回null。
目录结构:
com/thesimpzone/watch_pugs/watch_pugs/{all my class files}
META-INF/MANIFEST.MF
resources/generic/mouse.png
Content.java:
public abstract class Content {
protected Map<String, BufferedImage> images = new HashMap<String, BufferedImage>();
protected String prefix;
public Content(String prefix){
this.prefix = prefix;
}
protected void loadImage(String name){
System.out.println(name);
System.out.println(prefix);
String path = (prefix + name);
System.out.println(path);
String identifier = name.substring(0, name.lastIndexOf("."));
try{
InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path);
images.put(identifier, ImageIO.read(in));
}catch(IOException | ClassCastException e){
throw new RuntimeException("Image " + identifier + " at " + path + " could not be loaded.");
}
}
[...]
}
GenericContent.java:
public class GenericContent extends Content {
public GenericContent(){
super("resources/generic/");
this.loadContent();
}
@Override
public void loadContent() {
loadImage("mouse.png");
}
}
堆栈跟踪:
mouse.png
resources/generic/
resources/generic/mouse.png
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: input == null!
at javax.imageio.ImageIO.read(ImageIO.java:1348)
at com.thesimpzone.watch_pugs.watch_pugs.content.Content.loadImage(Content.java:29)
at com.thesimpzone.watch_pugs.watch_pugs.content.GenericContent.loadContent(GenericContent.java:17)
at com.thesimpzone.watch_pugs.watch_pugs.content.GenericContent.<init>(GenericContent.java:12)
at com.thesimpzone.watch_pugs.watch_pugs.Canvas.<init>(Canvas.java:45)
at com.thesimpzone.watch_pugs.watch_pugs.Framework.<init>(Framework.java:75)
at com.thesimpzone.watch_pugs.watch_pugs.Window.<init>(Window.java:50)
at com.thesimpzone.watch_pugs.watch_pugs.Window.<init>(Window.java:26)
at com.thesimpzone.watch_pugs.watch_pugs.Window$1.run(Window.java:60)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
我不知道为什么类加载器找不到图像。我查看了已编译的jar文件,该文件在那里,并且可以用油漆很好地打开,因此该文件还可以。我尝试了各种ClassLoader变体,包括getSystemClassLoader(),getClassLoader()和Content.class.getClassLoader();。以及getResourceAsStream(path)而不是getResource(path).openStream()。我已经尝试过在前缀上加上或不带前缀“ /”,所以我全都没主意,而Google也无济于事。另外,似乎我在定义“前缀”时所做的工作很尴尬,因此,如果有更好的方法,有人向我展示了如何做,我将很高兴。
谢谢。
调用时getResourceAsStream()
,所有内容都是相对包和绝对包的关系,您需要查找Content
与根包无关的东西。
类路径上没有“目录”,尤其是在.jar文件中,只有包
用最好的事情是Thread.currentThread().getContextClassloader().getResourceAsStream()
一个完全合格的包没有领先/
。
最好的原因是因为在应用程序容器内部,它们通常具有多个类加载器,因此您不必担心从哪个资源加载资源。
在您的情况下:
Thread.currentThread().getContextClassloader().getResourceAsStream("resources/generic/mouse.png");
如果使用此方法仍然遇到错误,.jar
则可能不是您认为的那样构建的,或者如果您是从IDE内部获取的,则可能不是在将内容复制resource/generic/
到类路径中。
我个人总是使用以下形式:
Thread.currentThread().getContextClassLoader().getResourceAsStream("path/to/resource/file.ext");
因为它总是可以在您调用它的地方以及您所处的类加载器中运行,并且明确表明它在哪里寻找它在寻找什么。
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