HarmonyOS 文件下载保存问题

通过request.downloadFile将网络音频资源下载到应用沙盒， 如何将沙盒里的音频文件保存到手机的“文件管理”

downloadFile(fileUrl:string, title:string, type:string){
  return new Promise<string>((resolve, reject) => {
    let context = getContext(this) as common.UIAbilityContext;
    let filesDir = context.filesDir;

    try {
      request.downloadFile(context, {
        url: fileUrl,
        filePath: filesDir + '/' + title + type
      }).then((downloadTask: request.DownloadTask) => {
        downloadTask.on('complete', () => {
          console.log(filesDir + '/' + title + type)
          resolve(filesDir + '/' + title + type) //此为下载成功返回的应用沙盒uri
        })
      }).catch((err: BusinessError) => {
        console.error(`Invoke downloadTask failed 2, code is ${err.code}, message is ${err.message}`);
        if (err.code === 13400002){
          resolve(filesDir + '/' + title + type)
        }else {
          resolve('fail')
        }
      });
    } catch (error) {
      let err: BusinessError = error as BusinessError;
      console.error(`Invoke downloadFile failed, code is ${err.code}, message is ${err.message}`);
      resolve('fail')
    }
  });
}