无法读取jar文件中的图像 [英] Cannot read an image in jar file

问题描述

当我构建一个jar文件并运行它时，由于找不到imageicon，它显示一个空指针异常

when i build a jar file and run it ,it shows a null pointer exception due to imageicon not found

new ImageIcon(getClass().getClassLoader().getResource("icons/exit.png")));

这是我运行jar文件时得到的错误

this is the error what i get when i run the jar file

Exception in thread "main" java.lang.NullPointerException
        at javax.swing.ImageIcon.<init>(Unknown Source)
        at mediaplayer.MediaPlayer.buildtoolbar(MediaPlayer.java:130)
        at mediaplayer.MediaPlayer.<init>(MediaPlayer.java:81)
        at mediaplayer.MediaPlayer.main(MediaPlayer.java:464)

但是当我在NetBeans中运行项目时，它的工作正常

But when i run the project in NetBeans, its working good

当我列出我的jar中的所有文件时，这是输出

This is the output when i list all the files inside my jar

META-INF/
META-INF/MANIFEST.MF
helliker/
helliker/id3/
icons/
mediaplayer/
Thumbs.db
exit.png
ff1.png
helliker/id3/BinaryParser.class
helliker/id3/CorruptHeaderException.class
helliker/id3/ID3Exception.class
helliker/id3/ID3FieldDataException.class
helliker/id3/ID3Tag.class
helliker/id3/ID3v1Tag.class
helliker/id3/ID3v2ExtendedHeader.class
helliker/id3/ID3v2Footer.class
helliker/id3/ID3v2FormatException.class
helliker/id3/ID3v2Frame.class
helliker/id3/ID3v2Frames.class
helliker/id3/ID3v2Header.class
helliker/id3/ID3v2Tag.class
helliker/id3/MP3Comparator.class
helliker/id3/MP3File.class
helliker/id3/MP3FileFilter.class
helliker/id3/MPEGAudioFrameHeader.class
helliker/id3/NoMPEGFramesException.class
helliker/id3/NullsoftID3GenreTable.class
helliker/id3/Playlist.class
helliker/id3/PlaylistException.class
helliker/id3/XingVBRHeader.class
icons/Thumbs.db
icons/exit.png
icons/ff1.png
icons/label.jpg
icons/openpl.gif
icons/pause1.png
icons/play1.png
icons/playlist.png
icons/rr.png
icons/rr1.PNG
icons/stop.png
label.jpg
mediaplayer/MediaPlayer$1.class
mediaplayer/MediaPlayer$PlaylistFilter.class
mediaplayer/MediaPlayer.class
mediaplayer/PlaylistManager$1.class
mediaplayer/PlaylistManager$MP3Filter.class
mediaplayer/PlaylistManager$PlaylistFilter.class
mediaplayer/PlaylistManager.class
mediaplayer/Settings.class
mediaplayer/TagEditor.class
mediaplayer/Thumbs.db
openpl.gif
pause1.png
play1.png
playlist.png
rr.png
rr1.PNG

推荐答案

在问题中如何实际构建jar文件时缺少一些信息，但是具有以下目录布局

There is missing some information in the question how the jar file is actually built, but with the following directory layout

├── bin
│   ├── com
│   │   └── example
│   │       └── ImageIconTest.class
│   └── icons
│       └── exit.png
└── src
    ├── MANIFEST.MF
    └── com
        └── example
            └── ImageIconTest.java

以及以下公司de in ImageIconTest.java

and the following code in ImageIconTest.java

package com.example;
import javax.swing.ImageIcon;

public class ImageIconTest {
   public void run() {
      ImageIcon ii = new ImageIcon(getClass().getClassLoader().getResource("icons/exit.png"));
      System.out.println(ii);
   }
   public static void main(String[] args) {
      ImageIconTest app = new ImageIconTest();
      app.run();
   }
}

您可以使用文件系统正确运行示例

you can properly run the sample from the file system with

$ java -classpath bin com.example.ImageIconTest

使用带有以下内容的MANIFEST.MF文件：

Using a MANIFEST.MF file with the following content:

Manifest-Version: 1.0
Main-Class: com.example.ImageIconTest

你可以将它打包成一个可执行的jar文件并从jar文件中运行它：

you can package it into an executable jar file and run it from the jar file:

$ jar cvfm app.jar src/MANIFEST.MF -C bin .
$ java -jar app.jar

这两种方法都运行正常，重要的细节是确保图标目录包含在适当位置的jar文件中。

Both approaches are working fine, the important detail is to make sure that the icon directory is included in the jar file at the proper location.

列出jar文件内容时，应该看起来像这样：

When listing the jar file contents, it should look like this:

  0 Tue Nov 06 12:27:56 CET 2012 META-INF/
107 Tue Nov 06 12:27:56 CET 2012 META-INF/MANIFEST.MF
  0 Tue Nov 06 12:27:56 CET 2012 com/
  0 Tue Nov 06 12:27:56 CET 2012 com/example/
950 Tue Nov 06 12:27:56 CET 2012 com/example/ImageIconTest.class
  0 Tue Nov 06 12:00:36 CET 2012 icons/
873 Tue Nov 06 12:00:36 CET 2012 icons/exit.png

注意图标目录的位置。

这篇关于无法读取jar文件中的图像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！