HarmonyOS 怎么获取文件公共目录，将文件下载放在公共目录下

根据文档提供的代码调用公共目录接口，代码如下：

if (!canIUse('SystemCapability.FileManagement.File.Environment.FolderObtain')) {
  console.error('this api is not supported on this device');
  return;
}
try {
  const downloadPath = Environment.getUserDownloadDir();
  console.info(`success to getUserDownloadDir: ${downloadPath}`);
  const documentsPath = Environment.getUserDocumentDir();
  console.info(`success to getUserDocumentDir: ${documentsPath}`);
  const desktopPath = Environment.getUserDesktopDir();
  console.info(`success to getUserDesktopDir: ${desktopPath}`);
} catch (error) {
  const err: BusinessError = error as BusinessError;
  console.error(`failed to get user dir, because: ${JSON.stringify(err)}`);
}

实际运行的时候会报错failed to get user dir, because: {“code”:801}