HarmonyOS 鸿蒙Next 上传图片失败求解，也存沙盒了就大神告知哪里出问题了 报错 Code: 13400001, message: file operation error

报错是说文件操作error，需要查看关于文件的操作方法，麻烦提供下FileUtil.getCacheDirPath方法，同时提供拷贝文件demo：

let path = getContext(this).filesDir+'/test.txt'
saveFileToCache(file, path) {
    // 创建缓存文件(当前是覆盖式创建)
    let cacheFile = fs.openSync(
      path,
      fs.OpenMode.WRITE_ONLY | fs.OpenMode.CREATE | fs.OpenMode.TRUNC
    )
    let buffer = new ArrayBuffer(4096);
    let currentOffset = file.offset;
    let lengthNeedToReed = file.length;
    let readOption = {
      offset: currentOffset,
      length: lengthNeedToReed > buffer.byteLength ? 4096 : lengthNeedToReed
    }
    while(true) {
      // 读取buffer容量的内容
      let readLength = fs.readSync(file.fd, buffer, readOption);
      // 写入buffer容量的内容
      fs.writeSync(cacheFile.fd, buffer, {length:readLength})
      // 判断后续内容 修改读文件的参数
      if (readLength < 4096) {
        break;
      }
      lengthNeedToReed -= readLength;
      readOption.offset += readLength;
      readOption.length = lengthNeedToReed > buffer.byteLength ? 4096 : lengthNeedToReed;
    }
    fs.close(cacheFile);
}