我为这个问题制定了一个变通方案，基本上包括在重试之前重建FormData。这感觉有点笨拙，但很有效。我首先通过请求选项中的“extra”Map传递重建所需的任何信息，以便拦截器可以访问它。下面是一些伪代码：

//original request
dioResponse = await dio.post(
  'http://my/api/endpoint',
  data: myOriginalFormData,
  options: Options(
    headers: myHeaders,
    extra: {'pathToMyFile': pathToMyFile},
  ),
);

//and in my interceptor I use it to construct a fresh FormData that has not been finalized
final FormData newFormData = FormData.fromMap({
  'file': await MultipartFile.fromFile(
       requestOptions.extra['pathToMyFile'],
       contentType: MediaType('application/json', 'json')),
});

//retry with the fresh FormData
return dio.request(
  requestOptions.path,
  data: newFormData,
  options: requestOptions,
  cancelToken: requestOptions.cancelToken,
  onReceiveProgress: requestOptions.onReceiveProgress,
  onSendProgress: requestOptions.onSendProgress,
  queryParameters: requestOptions.queryParameters,
);

有人对这种方法有什么想法吗？有什么主要的缺点吗？

似乎发送相同的表单数据而不完成最后一个请求的问题，通过以下方式解决了相同的问题：

static final Dio dio2 = Dio();

  static Future<dynamic> _retry(RequestOptions requestOptions) async {
    final options = new Options(
      method: requestOptions.method,
      headers: (await getHeaders()),
    );

    options.responseType = (ResponseType.json);
    Map<String, String>? data;
    try {
      data = Map.fromEntries(requestOptions.data?.fields);
    } catch (e) {}
    var res = dio2.request<dynamic>(
        requestOptions.baseUrl + requestOptions.path,
        data: data == null ? null : FormData.fromMap(data),
        queryParameters: requestOptions.queryParameters,
        options: options);

    return res;
  }

在你想重新发送相同请求的块中使用它：

handler.resolve(await _retry(response.requestOptions));