flutter json字符串类型和Map类型的相互转换以及、ajax网络请求

1、类型转换
	(1)引入
		import 'dart:convert';
		
	(2)转换
		json.encode(Map); 将Map类型转换成json字符串
		json.decode(json); 将json字符串类型转换成Map

2、网络请求
	(1)dart库搜索http按文档配置
	(2)引入
		import 'dart:convert' as convert;
		import 'package:http/http.dart' as http;
	(3)网络请求,在异步函数中设置
		
		get:
			var data= await http.get(url);
		    if (response.statusCode == 200) {
		        var res = convert.jsonDecode(data.body);
			
		 	 } else {
		    	print('Request failed with status: ${data.statusCode}.');
		    }
		
		post:
			var data = await http.post(url, body: {'key': 'value','key2','value2'});
			var res=convert.jsonDecode(response.body);

代码示例:

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

import 'package:flutter/material.dart';
import 'package:date_format/date_format.dart';
import 'package:flutter_cupertino_date_picker/flutter_cupertino_date_picker.dart';
import 'package:flutter_swiper/flutter_swiper.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:myflutter/page/me.dart';


class Home4 extends StatefulWidget {
  Home4({Key key}) : super(key: key);

  @override
  _Home2State createState() => _Home2State();
}

class _Home2State extends State<Home4> {
  String news='哈哈';
  @override
  void initState() { 
    super.initState();


  }
  var url="http://api.tianapi.com/txapi/ncov/index?key=4a8edfc8ac5eae9b0c5bf08157abba96";
  get() async{
      var response = await http.get(url);
      if (response.statusCode == 200) {
        var jsonResponse = convert.jsonDecode(response.body);
        setState(() {
          this.news=jsonResponse["msg"];
        });
        print(jsonResponse);
  } else {
    print('Request failed with status: ${response.statusCode}.');
    }
  }
  
  var url2="http://api.tianapi.com/txapi/ncov/index";
  post() async
  {
    var response = await http.post(url, body: {'key': '4a8edfc8ac5eae9b0c5bf08157abba96'});
    print(convert.jsonDecode(response.body));
  }

  @override
  Widget build(BuildContext context) {
    return Container(
       child: Column(
        mainAxisAlignment: MainAxisAlignment.start,
         children: <Widget>[
           
          RaisedButton(
            child: Text(news),
            color: Theme.of(context).accentColor,
            onPressed: (){
              get();
            },
          ),
          RaisedButton(
            child: Text('post'),
            color: Theme.of(context).accentColor,
            onPressed: (){
              post();
            },
          ),

       ]),
    );
  }
}


  


// 因为表单组件需要改变状态,所以要使用有状态组件