加入依赖：dio: ^3.0.9

class DioUtils {
  /// global dio object
   static Dio dio;
  /// default options
  static const int CONNECT_TIMEOUT = 10000;
  static const int RECEIVE_TIMEOUT = 3000;
  /// http request methods
  static const String GET = 'get';
  static const String NEWGET = 'newGet';
  static const String POST = 'post';
  static const String PUT = 'put';
  static const String PATCH = 'patch';
  static const String DELETE = 'delete';

 /// 创建 dio 实例对象
  static Future<Dio> createInstance() async {
if (dio == null) {
  /// 全局属性：请求前缀、连接超时时间、响应超时时间
  var options = BaseOptions(
      connectTimeout: 350000,
      receiveTimeout: 150000,
      responseType: ResponseType.json,
      validateStatus: (status) {
        // 不使用http状态码判断状态，使用AdapterInterceptor来处理（适用于标准REST风格）
        return true;
      },
      baseUrl: baseURL,
      headers: {
        'Accept': 'application/json,*/*',
        'Content-Type': 'application/json',
        //'token':''
      });

  dio = new Dio(options);
  dio.interceptors.add(InterceptorsWrapper(
    onRequest: (RequestOptions options) {
     /*. 拦截器请求 时 相关处理*/
      print('上传接口：${options.uri}');
    },
    onResponse: (e) {
     /* 拦截器 请求到数据后的 相关处理*/
      print('获取数据信息：$e');
    },
    onError: (e) {
      Navigator.pop(Router.navigatorState.currentState.context);
      _showErrorDialog('网络连接错误，请重试！');
      print('拦截器错误信息-->：$e');
    },
  ));
}

return dio;
 }

 /// 清空 dio 对象
 static clear() {
dio = null;
 }
///Get请求
  static void getHttp<T>(
   String url, {
parameters,
Function(T) onSuccess,
Function(String error) onError,
 }) async {
try {
  Dio dios = await createInstance()；
  Response response;
  response = await dios.get(
    url,
    queryParameters: parameters,
  ); //cancelToken: token
  var responseData = response.data;
  var i = responseData['msg'];
  if (responseData['code'] == 0) {
    onSuccess(responseData['data']);
  } else {
    onError(responseData['msg']);
  }
  print('get返回结果-->$responseData');
  print('get返回结果$i');
} catch (e) {
  print('请求出错：' + e.toString());
  onError(e.toString());
}
 }
///Post请求
 static void postHttp<T>(
String url, {
parameters,
Function(T) onSuccess,
Function(String error) onError,
 }) async {
try {
  Dio dios = await createInstance();
  Response response = await dios.post(
    url,
    data: parameters,
  ); //cancelToken: token
  var responseData = response.data;
  var i = responseData['msg'];
  if (responseData['code'] == 0) {
    onSuccess(responseData['data']);
  } else if (responseData['code'] == 200) {
    print('返回结果-->${responseData['code']}');
    onSuccess(responseData['data']);
  } else {
    print('指向这里');
    onError(responseData['msg']);
  }

  print('post返回结果$i');
} catch (e) {
  print('post返回结果x $e');
}
 }
/// request Get、Post 请求
//url 请求链接
//parameters 请求参数
//method 请求方式
//onSuccess 成功回调
//onError 失败回调
static void requestHttp<T>(String url,
  {parameters,
  method,
  Function(T t) onSuccess,
  Function(String error) onError}) async {
parameters = parameters ?? {};
method = method ?? 'GET';

if (method == DioUtils.GET) {
  getHttp(
    url,
    parameters: parameters,
    onSuccess: (data) {
      onSuccess(data);
    },
    onError: (error) {
      onError(error);
    },
  );
} else if (method == DioUtils.NEWGET) {
  newGetHttp(
    url,
    parameters: parameters,
    onSuccess: (data) {
      onSuccess(data);
    },
    onError: (error) {
      onError(error);
    },
  );
} else if (method == DioUtils.POST) {
  postHttp(
    url,
    parameters: parameters,
    onSuccess: (data) {
      onSuccess(data);
    },
    onError: (error) {
      onError(error);
    },
  );
} else if (method == DioUtils.PUT) {
  putHttp(
    url,
    parameters: parameters,
    onSuccess: (data) {
      onSuccess(data);
    },
    onError: (error) {
      onError(error);
    },
  );
} else if (method == DioUtils.DELETE) {
  deleteHttp(
    url,
    parameters: parameters,
    onSuccess: (data) {
      onSuccess(data);
    },
    onError: (error) {
      onError(error);
    },
  );
}
}

只是简单的封装了Dio请求，具体可以根据自身需要做进一步处理！！！
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