开始

数据接口为wanandroid的开放api,返回数据类型如下:

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{
"data": ...,
"errorCode": 0,
"errorMsg": ""
}

errorCode>=0时为网络请求成功,data则为返回的数据;

errorCode<0时为网络请求失败,errorMsg则为返回的错误信息;

普通网络请求

先导包

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import 'package:http/http.dart' as http;
import 'dart:convert';
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getBanners() async{
  String url = "http://www.wanandroid.com/banner/json";

  String errorMsg;
  int errorCode;
  var data;
  try {
    http.Response res = await http.get(url);
    if(res.statusCode!=200){
      errorMsg = "请求错误,错误码"+res.statusCode.toString();
      print(errorMsg);
      return;
    }
    Map<String, dynamic> map = json.decode(res.body);
    errorCode = map['errorCode'];
    errorMsg = map['errorMsg'];
    data = map['data'];
    // 这里实际上data是个list, List banners = data;
    // >=0才请求成功
    if(errorCode<0){
      print(errorMsg);
      return;
    }
    //这里偷懒直接打印数据
    print("data:" + data.toString());
  }catch(exception){
    print(exception.toString());
  }
}

请求结果(print可能打印的字符有上限)

返回结果

整个写下来的话,比较繁琐,需要先判断res.statusCode,以及数据的errorCode.然后再返回数据中的data部分.

那么接下来就稍微进行一下封装,直接返回了请求成功的数据(data部分)/错误信息(errorMsg或者请求过程中的其他错误信息)

目前对以下需求进行了封装

  • 一般的get请求
  • 一般的post请求

GET请求

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//String url
//Function callback              成功回调,参数为var data
//Map<String, String> params     请求\参数
//Map<String, String> headers    请求头
//Function errorCallback         错误回调,参数为String errorMsg
get(String url, Function callback,
    {Map<String, String> params,
    Map<String, String> headers,
    Function errorCallback}) async {}

普通使用

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HttpUtil.get("banner/json", (data) {
     List banners = data;
     print(banners.toString());
   });

带头带错误处理

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Map<String, String> headers = new Map();
  headers['Cookie'] = "我是cookie";
  HttpUtil.get("banner/json", (data) {
    List banners = data;
    print(banners.toString());
  }, errorCallback: (msg) {
    print(msg);
  }, headers: headers);

POST请求

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  _login() {
   
    Map<String,String> map = new Map();
    map['username'] = 'canhuah';
    map['password'] = 'a123456';

    HttpUtil.post('user/login', (data) {

//      _showMessage('登录 成功');
    },
        params: map,
        errorCallback: (msg) {
//     _showMessage(msg);
    });
  }

具体HttpUtil类

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import 'dart:async';
import 'package:http/http.dart' as http;

import 'dart:convert';

/*数据接口类型errorCode>0是接口请求成功
{
"data": ...,
"errorCode": 0,
"errorMsg": ""
}
*/

class Api {
  //这个BaseUrl自己更改
  static const String BaseUrl ="http://www.wanandroid.com/";
}

//这里只封装了常见的get和post请求类型
class HttpUtil {
  static const String GET = "get";
  static const String POST = "post";
  
  static void get(String url, Function callback,
      {Map<String, String> params,
      Map<String, String> headers,
      Function errorCallback}) async {
    //偷懒..
    if (!url.startsWith("http")) {
      url = Api.BaseUrl + url;
    }
    
    if (params != null && params.isNotEmpty) {
      StringBuffer sb = new StringBuffer("?");
      params.forEach((key, value) {
        sb.write("$key" + "=" + "$value" + "&");
      });
      String paramStr = sb.toString();
      paramStr = paramStr.substring(0, paramStr.length - 1);
      url += paramStr;
    }
    await _request(url, callback,
        method: GET,
        headers: headers,
        errorCallback: errorCallback);
  }

  static void post(String url, Function callback,
      {Map<String, String> params,
      Map<String, String> headers,
      Function errorCallback}) async {
    if (!url.startsWith("http")) {
      url = Api.BaseUrl + url;
    }
    await _request(url, callback,
		method: POST,
        headers: headers,
        params: params, 
        errorCallback: errorCallback);
  }

  static Future _request(String url, Function callback,
      {String method,
      Map<String, String> headers,
      Map<String, String> params,
      Function errorCallback}) async {
    String errorMsg;
    int errorCode;
    var data;
    try {
      Map<String, String> headerMap = headers == null ? new Map() : headers;
      Map<String, String> paramMap = params == null ? new Map() : params;

      http.Response res;
      if (POST == method) {
        res = await http.post(url, headers: headerMap, body: paramMap);
      } else {
        res = await http.get(url, headers: headerMap);
      }

      if (res.statusCode != 200) {
        errorMsg = "网络请求错误,状态码:"+res.statusCode.toString();	

        _handError(errorCallback, errorMsg);
        return;
      }

      //以下部分可以根据自己业务需求封装,这里是errorCode>=0则为请求成功,data里的是数据部分
      //记得Map中的泛型为dynamic
      Map<String, dynamic> map = json.decode(res.body);

      errorCode = map['errorCode'];
      errorMsg = map['errorMsg'];
      data = map['data'];

      // callback返回data,数据类型为dynamic
      //errorCallback中为了方便我直接返回了String类型的errorMsg
      if (callback != null) {
        if (errorCode >= 0) {
          callback(data);
        } else {
          _handError(errorCallback, errorMsg);
        }
      }
    } catch (exception) {
      _handError(errorCallback, exception.toString());
    }
  }

 
  static void _handError(Function errorCallback,String errorMsg){
    if (errorCallback != null) {
      errorCallback(errorMsg);
    }
    print("errorMsg :"+errorMsg);
  }
}