一、Flutter JSON 字符串和 Map 类型的转换

import 'dart:convert'

var mapData={"name":"张三","age":"20"};

var strData='{"name":"张三","age":"20"}';

print(json.encode(mapData)); //Map 转换成 Json 字符串

print(json.decode(strData)); //Json 字符串转化成 Map 类型

二、使用 官方http 库进行网络请求

请参考官方文档：https://pub.dev/packages/http

三、Flutter Dio 库

dio 是一个强大的 Dart Http 请求库，支持 Restful API、FormData、拦截器、请

求取消、Cookie 管理、文件上传/下载、超时、自定义适配器等...

https://pub.dev/packages/dio

https://github.com/flutterchina/dio/blob/master/README-ZH.md

官方http 案例代码-----------下面有dio http 代码案例

import 'package:flutter/material.dart';

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

import 'dart:convert';

class HttpPage extends StatefulWidget {

HttpPage({Key key}) : super(key: key);

_HttpDemoState createState() => _HttpDemoState();

}

class _HttpDemoState extends State {

List _list=[];

@override

initState() {

// TODO: implement initState

super.initState();

this._getData();

}

_getData() async{

var apiUrl="http://a.itying.com/api/productlist";

var result=await http.get(apiUrl);

if(result.statusCode==200){

print(result.body);

setState(() {

this._list=json.decode(result.body)["result"];

});

}else{

print("失败${result.statusCode}");

}

}

@override

Widget build(BuildContext context) {

return Scaffold(

appBar: AppBar(

title: Text("请求数据Demo"),

),

body: this._list.length>0?ListView(

children: this._list.map((value){

return ListTile(

title: Text(value["title"]),

);

}).toList(),

):Text("加载中...")

);

}

}

dio http 代码案例

dio: ^3.0.9

import 'dart:convert';

import 'package:flutter/material.dart';

import 'package:dio/dio.dart';

class UpDown extends StatefulWidget{

UpDown({Key key});

_UpDown createState() => _UpDown();

}

class _UpDown extends State {

@override

var list = [];

var page = 1;

var pageFlag = true;

var _scrollController = ScrollController();

initState() {

super.initState();

_getData();

_scrollController.addListener(() { // 上拉加载

var _scrollTop = _scrollController.position.pixels; //获取滚动条下拉的距离

var _scrollHeight = _scrollController.position.maxScrollExtent; //获取整个页面的高度

if(_scrollTop >= _scrollHeight - 20) {

_getData();

}

});

}

// 获取数据

_getData() async{

if(pageFlag == false) return;

var response = await Dio().get('http://www.phonegap100.com/appapi.php?a=getPortalList&catid=20&page=${page}');

var res = json.decode(response.data)['result'];

setState(() {

list.addAll(res);

page++;

});

if(res.length < 20) {

setState(() {

pageFlag = false;

});

}

}

// 下拉刷新

Future _onRefresh() async {

await Future.delayed(

Duration(

milliseconds: 2000), () {

list = [];

page = 1;

_getData();

});

}

Widget build(BuildContext context) {

// TODO: implement build

return Scaffold(

appBar: AppBar(title: Text('上拉加载-下拉刷新'),),

body: list.length > 0 ? RefreshIndicator(

onRefresh: _onRefresh,

child: ListView.builder(

controller: _scrollController,

itemCount: list.length,

itemBuilder: (context, index) {

return Column(

children: [

Container(

padding: EdgeInsets.only(top: 5, bottom: 5, left: 5),

alignment: Alignment.centerLeft,

child: Text('${list[index]['title']}', maxLines: 1, overflow: TextOverflow.ellipsis),

),

Divider(),

index == list.length - 1 ? getMoreTips(flag: this.pageFlag) : SizedBox()

],

);

},

),

) : getMoreTips(flag: this.pageFlag)

);

}

}

class getMoreTips extends StatelessWidget{ // 底部的转圈和文字

var flag = true;

getMoreTips({Key key, this.flag}) : super(key: key);

@override

Widget build(BuildContext context) {

// TODO: implement build

return Center(

child: flag ? Row(

mainAxisAlignment: MainAxisAlignment.center,

children: [

Text('正在加载...'),

SizedBox(width: 10),

CircularProgressIndicator(strokeWidth: 2)

],

) : Column(

mainAxisAlignment: MainAxisAlignment.center,

children: [

Text('没有更多数据了'),

SizedBox(height: 10),

],

),

);

}

}

Dio封装 带拦截器

import 'dart:convert';

import 'package:dio/dio.dart';

import 'utils.dart';

var dio = Dio();

interceptors () async{

// dio.options.contentType = 'application/json;charset=UTF-8';

// dio.options.headers = {'testHeader':'aaaa'};

var tokens = await Storage.getString('token');

dio.options.baseUrl = '';

dio.options.connectTimeout = 15000;

dio.options.receiveTimeout = 15000;

dio.interceptors.add(

InterceptorsWrapper(

onRequest: (options) async {

// print("method = ${options.method.toString()}");

// print("url = ${options.uri.toString()}");

// print("headers = ${options.headers}");

// print("params = ${options.queryParameters}");

// 此处可网络请求之前做相关配置，比如会所有请求添加token

// options.queryParameters['token'] = 'testtoken123443423';

// options.headers["token"] = "testtoken123443423";

// if (tokens == null) {

// dio.lock();

// return dio.get('/token').then((e) {

//

// options.queryParameters['token'] = e.data['data']['token'];

// Storage.setString('token', {token: e.data['data']['token']});

//

// return options;

// }).whenComplete(() => dio.unlock());

// } else {

// options.queryParameters['token'] = 'testtoken123443423';

// return options;

// }

return options;

},

onResponse: (response) {

//此处拦截工作在数据返回之后，可在此对dio请求的数据做二次封装或者转实体类等相关操作

return response;

},

onError: (error) {

//处理错误请求

return error;

}),

);

}

class DioHttp {

static const downloadUrl = 'https://dev1.mifengff.com/obhcx4';

// DioHttp.get(

// 'http://www.phonegap100.com/appapi.php?a=getPortalList',

// queryParameters: {

// 'catid': 20, 'page': page

// },

// success: (e) {

// setState(() {list.addAll(e);page++;});

// if(e.length < 20) {setState(() {pageFlag = false;});}

// });

static get (url, {queryParameters, success = '', error = '', headers = '', requests = '', statusCodes = ''}) async{

interceptors();

try{

var response = await dio.get(dio.options.baseUrl + url, queryParameters: queryParameters ?? {});

if(headers != '') {headers(response.headers);}

if(requests != '') {requests(response.request);}

if(statusCodes != '') {statusCodes(response.statusCode);}

if(response.statusCode == 200) {

var res = json.decode(response.data)['result'];

if(success != '') {success(res);}

} else {

if(error != '') {error(response);}

throw Exception('erroor: $response');

}

} catch (e) {

formatError(e);

throw Exception('erroor: $e');

}

}

static post (url, {data, success = '', error = '', headers = '', requests = '', statusCodes = '', onSendProgress}) async{

interceptors();

try{

var response = await dio.post(dio.options.baseUrl + url, data: data ?? {}, onSendProgress: onSendProgress ?? () {});

if(headers != '') {headers(response.headers);}

if(requests != '') {requests(response.request);}

if(statusCodes != '') {statusCodes(response.statusCode);}

if(response.statusCode == 200) {

var res = json.decode(response.data)['result'];

if(success != '') {success(res);}

} else {

if(error != '') {error(response);}

throw Exception('erroor: $response');

}

} catch (e) {

formatError(e);

throw Exception('erroor: $e');

}

}

static download (url, saveUrl, {success, error, onReceiveProgress}) async{

interceptors();

try{

var response = await dio.download(dio.options.baseUrl + url, saveUrl, onReceiveProgress: onReceiveProgress ?? () {});

if(response.statusCode == 200) {

var res = json.decode(response.data)['result'];

if(success != '') {success(res);}

} else {

if(error != '') {error(response);}

throw Exception('erroor: $response');

}

} catch (e) {

formatError(e);

throw Exception('erroor: $e');

}

}

static formData (url, data, {success, error}) async{

interceptors();

// var formData = FormData.fromMap({

// 'name': 'wendux',

// 'age': 25,

// });

try{

var response = await dio.post(dio.options.baseUrl + url, data: data ?? {});

if(response.statusCode == 200) {

var res = json.decode(response.data)['result'];

if(success != '') {success(res);}

} else {

if(error != '') {error(response);}

throw Exception('erroor: $response');

}

} catch (e) {

formatError(e);

throw Exception('erroor: $e');

}

}

}

// error统一处理

void formatError(DioError e) {

if (e.type == DioErrorType.CONNECT_TIMEOUT) {

print("连接超时");

} else if (e.type == DioErrorType.SEND_TIMEOUT) {

print("请求超时");

} else if (e.type == DioErrorType.RECEIVE_TIMEOUT) {

print("响应超时");

} else if (e.type == DioErrorType.RESPONSE) {

print("出现异常404 503");

} else if (e.type == DioErrorType.CANCEL) {

print("请求取消");

} else {

print("未知错误");

}

}