downloadGroupSharedFile method
~english Downloads the shared file of the group.
Note: The callback is only used for progress callback.
Param groupId The group ID.
Param fileId The ID of the shared file.
Param savePath The local path of the shared file.
Throws A description of the exception. See ChatError. ~end
~chinese 下载指定的群组共享文件。
Param groupId 群组 ID。
Param fileId  共享文件的 ID。
Param savePath 共享文件的本地路径。
Throws 如果有异常会在此抛出,包括错误码和错误信息,详见 ChatError。 ~end
Implementation
Future<void> downloadGroupSharedFile({
  required String groupId,
  required String fileId,
  required String savePath,
}) async {
  Map req = {'groupId': groupId, 'fileId': fileId, 'savePath': savePath};
  Map result = await _channel.invokeMethod(
      ChatMethodKeys.downloadGroupSharedFile, req);
  try {
    ChatError.hasErrorFromResult(result);
  } on ChatError catch (e) {
    throw e;
  }
}