详解flutter之网络请求dio，请求，拦截器简单示例

import 'package:dio/dio.dart';import 'dart:async';import 'dart:io';import './apidomain.dart';import './httpHeaders.dart';import 'package:shared_preferences/shared_preferences.dart';class DioUtil{  static Dio dio = new Dio();  //请求部分  static Future request(url,{formData})async{    try{      Response response;      dio.options.headers = httpHeaders;      dio.options.contentType = ContentType.parse("application/json;charset=UTF-8");      if(formData == null){        response = await dio.post(serviceUrl+url);      }else{        response = await dio.post(serviceUrl+url,data:formData);      }      if(response.statusCode == 200){        return response;      }else{        throw Exception("接口异常R");      }    }catch(e){      print("网络出现错误${e}");    }  }  //拦截器部分  static tokenInter(){    dio.interceptors.add(InterceptorsWrapper(      onRequest:(RequestOptions options){        // 在发送请求之前做一些预处理        //我这边是在发送前到SharedPreferences（本地存储）中取出token的值，然后添加到请求头中        //dio.lock()是先锁定请求不发送出去，当整个取值添加到请求头后再dio.unlock()解锁发送出去        dio.lock();        Future<dynamic> future = Future(()async{          SharedPreferences prefs =await SharedPreferences.getInstance();          return prefs.getString("loginToken");        });        return future.then((value) {          options.headers["Authorization"] = value;          return options;        }).whenComplete(() => dio.unlock()); // unlock the dio      },      onResponse:(Response response) {        // 在返回响应数据之前做一些预处理        return response; // continue      },      onError: (DioError e) {        // 当请求失败时做一些预处理        return e;//continue      }    ));  }}

const httpHeaders={  'Accept': 'application/json, text/plain, */*',  'Authorization': '666',  'Content-Type': 'application/json;charset=UTF-8',  'Origin': 'http://localhost:8080',  'Referer': 'http://localhost:8080/',  'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36',};

const serviceUrl = 'http://39.xxx.xxx.xx:8080';