HarmonyOS 下载文件到内部存储报错：401

文件管理所展示目录仅能通过picker保存文件进去，参考：

https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/save-user-file-V5

//如下代码可以保存一个空图片到文件管理器，获取空文件路径之后把应用沙箱里的图片复制到空文件

async function func(){
  let uris:String = ""
  try {
    const DocumentSaveOptions = new picker.DocumentSaveOptions(); // 创建文件管理器保存选项实例

    DocumentSaveOptions.newFileNames = ["DocumentSaveOptions01.txt"]; // 保存文件名（可选），方括号里的文件名自定义，每次不能重复，设备里已有这个文件的话，名字就需要改个不一样的，不然接口会报错
    const DocumentViewPicker = new picker.DocumentViewPicker();
    try {
      let DocumentSaveResult = await DocumentViewPicker.save(DocumentSaveOptions);
      if (DocumentSaveResult != undefined) {
        uris = DocumentSaveResult[0];
        console.info('photoViewPicker.save to file succeed and uris are:' + uris);
      }
    } catch (error) {
      let err: BusinessError = error as BusinessError;
      console.error(`[picker] Invoke photoViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
    }
  } catch (error) {
    let err: BusinessError = error as BusinessError;
    console.info("[picker] photoViewPickerSave error = " + JSON.stringify(err));
  }
  try{
    let path = getContext().filesDir+"/index.html" //需要保存的图片的路径

    let file = fs.openSync(path,fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
    let bytes=GlobalThis.context?.resourceManager.getRawFileContentSync('index.html');
    fs.writeSync(file.fd,bytes?.buffer);
    console.info("photoViewPickerSave uris = " + uris);
    let file2 = fs.openSync(uris+"",fs.OpenMode.READ_WRITE)
    fs.copyFileSync(file.fd,file2.fd)
    fs.closeSync(file)
    fs.closeSync(file2)
  }catch (error) {
    let err: BusinessError = error as BusinessError;
    console.error(`[picker] Invoke photoViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
  }
}