private void CopyAssets(String assetDir, String dir) {
    String[] files;
    try {
      // 获得Assets一共有几多文件
      files = this.getResources().getAssets().list(assetDir);
    } catch (IOException e1) {
      return;
    }
    File mWorkingPath = new File(dir);
    // 如果文件路径不存在
    if (!mWorkingPath.exists()) {
      // 创建文件夹
      if (!mWorkingPath.mkdirs()) {
        // 文件夹创建不成功时调用
      }
    }
    for (int i = 0; i < files.length; i++) {
      try {
        // 获得每个文件的名字
        String fileName = files[i];
        // 根据路径判断是文件夹还是文件
        if (!fileName.contains(".")) {
          if (0 == assetDir.length()) {
            CopyAssets(fileName, dir + fileName + "/");
          } else {
            CopyAssets(assetDir + "/" + fileName, dir + "/"
                + fileName + "/");
          }
          continue;
        }
        File outFile = new File(mWorkingPath, fileName);
        if (outFile.exists())
          outFile.delete();
        InputStream in = null;
        if (0 != assetDir.length())
          in = getAssets().open(assetDir + "/" + fileName);
        else
          in = getAssets().open(fileName);
        OutputStream out = new FileOutputStream(outFile);
        // Transfer bytes from in to out
        byte[] buf = new byte[1024];
        int len;
        while ((len = in.read(buf)) > 0) {
          out.write(buf, 0, len);
        }
        in.close();
        out.close();
      } catch (FileNotFoundException e) {
        e.printStackTrace();
      }
      catch (IOException e) {
        e.printStackTrace();
      }
    }
}