我现在采用的网络框架是基于dio的。
线上工具类：

import 'package:dio/dio.dart';
import 'package:http_parser/http_parser.dart';
import 'package:yxk_app/constant/functions.dart';
import 'package:yxk_app/net/request_api.dart';
import 'package:yxk_app/utils/data_utils.dart';
import 'package:yxk_app/utils/log_utils.dart';

/// 网络请求
class RequstUtil {
  // token值
  static String token;

  // 初始化
  static final Dio _dio = new Dio(new BaseOptions(
      method: RequestApi.methodGet,
      baseUrl: RequestApi.baseUrl,
      connectTimeout: RequestApi.connectTimeout,
      receiveTimeout: RequestApi.receiveTimeout,
      followRedirects: true));

  /// 请求
  ///
  /// 必填字段:
  /// method 请求方法，如 RequestApi.methodGet
  /// uri 请求地址
  /// isBody 表单格式为false、json格式为true
  ///
  /// 可选字段：
  /// key 服务端返回数据中需要取得字段，不设置的话默认是同级code的data值
  /// responceSuccess 返回成功数据回调
  /// responceError 返回失败数据回调
  static doRequest(String method, String uri, bool isBody,
      {Map<String, dynamic> body,
      String key,
      ResponceSuccess responceSuccess,
      ResponceError responceError}) async {
    _httpJson(method, uri, isBody, data: body).then((resp) {
      doResponse(resp,
          key: key,
          responceSuccess: responceSuccess,
          responceError: responceError);
    });
  }

  /// 文件上传  返回json数据为字符串
  static Future putFile(String uri, String filePath,
      {ResponceSuccess responceSuccess, ResponceError responceError}) {
    String name =
        filePath.substring(filePath.lastIndexOf("/") + 1, filePath.length);

    FormData formData = FormData.fromMap({
      "multipartFile": MultipartFile.fromFile(filePath,
          filename: name, contentType: MediaType.parse("multipart/form-data")),
    });

    var enToken = token == null ? "" : Uri.encodeFull(token);
    return _dio
        .put<Map<String, dynamic>>("$uri?token=$enToken", data: formData)
        .then((resp) {
      doResponse(resp,
          responceSuccess: responceSuccess, responceError: responceError);
    });
  }

  /// 请求数据
  static Future<Response<Map<String, dynamic>>> _httpJson(
      String method, String uri, bool isBody,
      {Map<String, dynamic> data}) {
    Log.d('请求地址:$uri\n请求参数:$data');

    Options op = Options(method: method, headers: {
      "Content-Type": "application/json",
      "Accept": "application/json"
    });

    if (isBody) {
      return _dio.request<Map<String, dynamic>>(uri,
          data: data ?? Map<String, dynamic>(), options: op);
    } else {
      return _dio.request<Map<String, dynamic>>(uri,
          queryParameters: data ?? Map<String, dynamic>(), options: op);
    }
  }

  /// 返回数据统一处理
  static void doResponse(Response<Map<String, dynamic>> resp,
      {String key,
      ResponceSuccess responceSuccess,
      ResponceError responceError}) {
    LogicError error = LogicError("-1", "未知异常");

    // 打印日志
    Log.d('返回数据:$resp');

    // 回调监听
    if (null != resp.data && null != resp.data['code']) {
      if (resp.data["code"] == "0" || resp.data["code"] == "200") {
        // 成功
        if (null != responceSuccess)
          responceSuccess(
              !StringUtils.isEmpty(key) ? resp.data["data"][key] : resp.data);
        return;
      } else {
        // 失败
        error = new LogicError(resp.data["code"], resp.data['msg']);

        /// token失效 重新登录  后端定义的code码
        if (resp.data["code"] == RequestApi.tokenIllegalCode) {
          // todo 退出登录界面

        }
      }
    }
    if (null != responceError) responceError(error);
  }
}

/// 异常类
class LogicError {
  final String errorCode;
  final String msg;

  LogicError(this.errorCode, this.msg);
}

enum PostType { json, form, file }

api相关类:

/// 请求api
class RequestApi {
  /// 方法
  static final String methodGet = "get";
  static final String methodPost = "post";
  static final String methodPut = "put";
  static final String methodDellete = "delete";

  /// 网络请求配置信息
  static final String baseUrl = "${基础域名}"; // 基础域名
  static final int connectTimeout = 10 * 1000; // 连接超时时间
  static final int receiveTimeout = 10 * 1000; // 接收超时时间

  /// 错误信息
  static final String tokenIllegalCode = "-99"; // token失效code码

  /// 接口
  static String login = "${你自己的接口}"; // 用户登录
}

整体比较简单，注释也很全了，错误异常是一个异常类，正常的返回可能存在bool、String、Object、Map、List等等类型，这些自己可以采用dynamic提取最终数据，然后直接转换就可以了，也比较简单。