android – 如何从我的.apk文件中打包的jar文件中加载一个类？

我试图从我的.apk文件的/ assets目录中的jar文件加载接口的插件实现.我能够让它工作的唯一方法是将jar文件解压缩到私有外部存储器,然后将该文件传递给DexClassLoader.

这有效,但为什么jar必须存在于两个地方(.apk和私人外部存储)？ DexClassLoader必须以文件路径作为参数.

有没有办法给它一个直接路径到/ assets文件夹中的文件,这样我就不必使用外部存储来获取已存在的文件的额外副本？

以下是相关的代码段：

// somewhere in my main Activity ...
  final File aExtractedDexFile = new File(getDir("dex",Context.MODE_PRIVATE),LIBRARY_DEX_JAR);
  extractDexTo(aExtractedDexFilE);
  loadLibraryProvider(aExtractedDexFilE);

和

/** Extract the jar file that contains the implementation class.dex and place in private storage */
private void extractDexTo(File tJarInternalStoragePath) {
  BufferedInputStream aJarInputStream = null;
  OutputStream aDexOutputStream = null;

  try {
    aJarInputStream = new BufferedInputStream(getAssets().open(LIBRARY_DEX_JAR));
    aJarOutputStream = new bufferedoutputstream(new FiLeoutputStream(tJarInternalStoragePath));
    byte[] buf = new byte[BUF_SIZE];
    int len;
    while ((len = aJarInputStream.read(buf,BUF_SIZE)) > 0)
    {
      aJarOutputStream.write(buf,len);
    }
    aJarOutputStream.close();
    aJarInputStream.close();
  } catch (IOException E) {
    if (aDexOutputStream != null) {
      try {
        aJarOutputStream.close();
      } catch (IOException ioE) {
        ioe.printStackTrace();
      }
    }

    if (aJarInputStream != null) {
      try {
        aJarInputStream.close();
      } catch (IOException ioE) {
        ioe.printStackTrace();
      }
    }
  }
}

和

/** Use DexClassLoader to load the classes from LibraryProvider */
private void loadLibraryProvider(File tFilE) {
  // Internal storage where the DexClassLoader writes the optimized dex file to.
  final File aOptimizedDexOutputPath = getDir("outdex",Context.MODE_PRIVATE);

  // Initialize the class loader with the secondary dex file.
  DexClassLoader cl = new DexClassLoader(tFile.getAbsolutePath(),aOptimizedDexOutputPath.getAbsolutePath(),null,getClassLoader());
  Class<?> aLibProviderClazz = null;

  try {
    // Load the library class from the class loader.
    aLibProviderClazz = cl.loadClass(LIBRARY_PROVIDER_CLASS);      
    sLibraryProvider = (LibraryInterfacE) aLibProviderClazz.newInstance();
  } catch (Exception exception) {
    // Handle exception gracefully here.
    exception.printStackTrace();
  }
}