HarmonyOS webview中h5保存网络图片到相册， 下载excel格式的文件需要调用什么方法

当前下载保存可以参考以下demo：

// 下载保存
downloadSave() {
  let context = GlobalContext.getContext().getObject("UIAbilityContext") as common.UIAbilityContext
  let filePath = context.filesDir + "/test5.xlsx";
  let url = "http://www.huaiwei.com"
  try {
    request.downloadFile(context, { url: url, filePath: filePath }).then((data: request.DownloadTask) => {
      let downloadTask: request.DownloadTask = data;
      downloadTask.on('complete', () => {
        console.info('download complete');
        let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
        let arrayBuffer = new ArrayBuffer(4096000);
        let readLen = fs.readSync(file.fd, arrayBuffer);
        let buf = buffer.from(arrayBuffer, 0, readLen);
        console.info(`content of File: ${buf.toString()}`);
        let writeLen = fs.writeSync(file.fd, arrayBuffer);
        fs.closeSync(file);
        const documentSaveOptions = new picker.DocumentSaveOptions();
        // 创建文件管理器选项实例
        documentSaveOptions.newFileNames = ["1.xlsx"];
        // 保存文件名（可选）
        documentSaveOptions.fileSuffixChoices = ['xlsx'];
        // 保存文件类型（可选）
        let uris: Array<string> = [];
        const documentViewPicker = new picker.DocumentViewPicker();
        // 创建文件选择器实例
        documentViewPicker.save(documentSaveOptions).then((documentSaveResult: Array<string>) => {
          uris = documentSaveResult;
          console.info('documentViewPicker.save to file succeed and uris are:' + uris);
          let uri = uris[0];
          let file2 = fs.openSync(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
          let writeLen2 = fs.writeSync(file2.fd, arrayBuffer);
          fs.closeSync(file2);
        }).catch((err: BusinessError) => {
          console.error(`Invoke documentViewPicker.save failed, code is ${err.code}, message is ${err.message}`);
        })
      })
      let failCallback = () => {
        console.info('Download task fail.');
      };
      downloadTask.on('fail', failCallback);
    }).catch((err: BusinessError) => {
      console.error(`downLoadFileTask failed, code is ${err.code}, message is ${err.message}`);
    });
  } catch (error) {
    console.error(`downLoadFileTask failed, code is ${error.code}, message is ${error.message}`);
  }
}
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