Flutter 网络请求封装之Dio（Cookie管理、添加拦截器、下载文件、异常处理、取消请求等）

- [Dio相关](https://cloud.tencent.com/developer)
- [封装开始](https://cloud.tencent.com/developer)
- [get请求](https://cloud.tencent.com/developer)
- [post请求](https://cloud.tencent.com/developer)
        - [post Form表单](https://cloud.tencent.com/developer)
- [异常处理](https://cloud.tencent.com/developer)
- [Cookie管理](https://cloud.tencent.com/developer)
- [添加拦截器](https://cloud.tencent.com/developer)
- [下载文件](https://cloud.tencent.com/developer)
- [取消请求](https://cloud.tencent.com/developer)
- [Https证书校验](https://cloud.tencent.com/developer)
- [调用示例](https://cloud.tencent.com/developer)
- [完整代码](https://cloud.tencent.com/developer)

dependencies:
  dio: ^3.0.9

import 'package:dio/dio.dart';
void getHttp() async {
  try {
    Response response = await Dio().get("http://www.baidu.com");
    print(response);
  } catch (e) {
    print(e);
  }
}

class HttpUtil {
  static HttpUtil instance;
  Dio dio;
  BaseOptions options;

  CancelToken cancelToken = new CancelToken();

  static HttpUtil getInstance() {
    if (null == instance) instance = new HttpUtil();
    return instance;
  }
}

  /*
   * config it and create
   */
  HttpUtil() {
    //BaseOptions、Options、RequestOptions 都可以配置参数，优先级别依次递增，且可以根据优先级别覆盖参数
    options = new BaseOptions(
      //请求基地址,可以包含子路径
      baseUrl: "http://www.google.com",
      //连接服务器超时时间，单位是毫秒.
      connectTimeout: 10000,
      //响应流上前后两次接受到数据的间隔，单位为毫秒。
      receiveTimeout: 5000,
      //Http请求头.
      headers: {
        //do something
        "version": "1.0.0"
      },
      //请求的Content-Type，默认值是"application/json; charset=utf-8",Headers.formUrlEncodedContentType会自动编码请求体.
      contentType: Headers.formUrlEncodedContentType,
      //表示期望以那种格式(方式)接受响应数据。接受4种类型 `json`, `stream`, `plain`, `bytes`. 默认值是 `json`,
      responseType: ResponseType.json,
    );

    dio = new Dio(options);
  }

RequestOptions requestOptions=new RequestOptions(
        baseUrl: "http://www.google.com/aa/bb/cc/"
      );

  /*
   * get请求
   */
  get(url, {data, options, cancelToken}) async {
    Response response;
    try {
      response = await dio.get(url, queryParameters: data, options: options, cancelToken: cancelToken);
      print('get success---------${response.statusCode}');
      print('get success---------${response.data}');

//      response.data; 响应体
//      response.headers; 响应头
//      response.request; 请求体
//      response.statusCode; 状态码

    } on DioError catch (e) {
      print('get error---------$e');
      formatError(e);
    }
    return response.data;
  }

  /*
   * post请求
   */
  post(url, {data, options, cancelToken}) async {
    Response response;
    try {
      response = await dio.post(url, queryParameters: data, options: options, cancelToken: cancelToken);
      print('post success---------${response.data}');
    } on DioError catch (e) {
      print('post error---------$e');
      formatError(e);
    }
    return response.data;
  }

FormData formData = FormData.from({
    "name": "wendux",
    "age": 25,
  });
response = await dio.post("/info", data: formData);

  /*
   * error统一处理
   */
  void formatError(DioError e) {
    if (e.type == DioErrorType.CONNECT_TIMEOUT) {
      // It occurs when url is opened timeout.
      print("连接超时");
    } else if (e.type == DioErrorType.SEND_TIMEOUT) {
      // It occurs when url is sent timeout.
      print("请求超时");
    } else if (e.type == DioErrorType.RECEIVE_TIMEOUT) {
      //It occurs when receiving timeout
      print("响应超时");
    } else if (e.type == DioErrorType.RESPONSE) {
      // When the server response, but with a incorrect status, such as 404, 503...
      print("出现异常");
    } else if (e.type == DioErrorType.CANCEL) {
      // When the request is cancelled, dio will throw a error with this type.
      print("请求取消");
    } else {
      //DEFAULT Default error type, Some other Error. In this case, you can read the DioError.error if it is not null.
      print("未知错误");
    }
  }

dependencies:
 dio_cookie_manager: ^1.0.0

import 'package:cookie_jar/cookie_jar.dart';
import 'package:dio/dio.dart';
import 'package:dio_cookie_manager/dio_cookie_manager.dart';

//Cookie管理
dio.interceptors.add(CookieManager(CookieJar()));

    dio = new Dio(options);
    
    //添加拦截器
    dio.interceptors.add(InterceptorsWrapper(onRequest: (RequestOptions options) {
      print("请求之前");
      // Do something before request is sent
      return options; //continue
    }, onResponse: (Response response) {
      print("响应之前");
      // Do something with response data
      return response; // continue
    }, onError: (DioError e) {
      print("错误之前");
      // Do something with response error
      return e; //continue
    }));

  /*
   * 下载文件
   */
  downloadFile(urlPath, savePath) async {
    Response response;
    try {
      response = await dio.download(urlPath, savePath,onReceiveProgress: (int count, int total){
        //进度
        print("$count $total");
      });
      print('downloadFile success---------${response.data}');
    } on DioError catch (e) {
      print('downloadFile error---------$e');
      formatError(e);
    }
    return response.data;
  }

  /*
   * 取消请求
   *
   * 同一个cancel token 可以用于多个请求，当一个cancel token取消时，所有使用该cancel token的请求都会被取消。
   * 所以参数可选
   */
  void cancelRequests(CancelToken token) {
    token.cancel("cancelled");
  }

String PEM="XXXXX"; // certificate content
(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate  = (client) {
    client.badCertificateCallback=(X509Certificate cert, String host, int port){
        if(cert.pem==PEM){ // Verify the certificate
            return true;
        }
        return false;
    };
};

(dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate  = (client) {
    SecurityContext sc = new SecurityContext();
    //file is the path of certificate
    sc.setTrustedCertificates(file);
    HttpClient httpClient = new HttpClient(context: sc);
    return httpClient;
};

      var response = await HttpUtil().get("http://www.baidu.com");
      print(response.toString());