flutter stream and streambuilder 详解

https://stackoverflow.com/questions/60487025/flutter-streambuilder-refresh

// learn from  https://www.digitalocean.com/community/tutorials/flutter-futures-and-streams-dart


import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert'; //This allows us to convert the returned JSON data into something Dart can use.

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  Future GetCountry(country) async {
    //String countryUrl = 'https://restcountries.eu/rest/v2/name/$country';
    String countryUrl = 'http://176.122.178.74:3000/foods';

    // http
    //   .get(countryUrl)
    //   // .then((response) => jsonDecode(response.body)[0]['name'])
    //   .then((response) => jsonDecode(response.body))
    //   .then((decoded) => print(decoded))
    //   .catchError((error) => throw(error));

    final response = await http.get('http://176.122.178.74:3000/foods');
    // final jsonResponse = json.decode(response.body);
    Map<String, dynamic> map = json.decode(response.body);
    Map<String, dynamic> data = map["foods"];  


    for (final name in data.keys) {
      final value = data[name];
      print('$name,$value'); // prints entries like "AED,3.672940"
    }
  


    // Map<String, dynamic> data1 = data["icecream"];

    // print(data1["name"]);
    //List<dynamic> data1 = data["icecream"];

    // final Map<String, dynamic> parsedmap = jsonDecode(jsonResponse);
    // for(var u in jsonResponse){
    //   print(u);
    // }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: MaterialButton(
          onPressed: () => GetCountry('japan'),
          child: Container(
            color: Colors.blue,
            padding: EdgeInsets.all(15),
            child: Text('Get Country', style: TextStyle(color: Colors.white))),
        ),
      ),
    );
  }
}

// learn from https://www.digitalocean.com/community/tutorials/flutter-futures-and-streams-dart

import 'package:flutter/material.dart';

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

import 'dart:convert'; //This allows us to convert the returned JSON data into something Dart can use.

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {

@override

Widget build(BuildContext context) {

return MaterialApp(

title: 'Flutter Demo',

home: MyHomePage(),

);

}

class MyHomePage extends StatelessWidget {

Future GetCountry(country) async {

//String countryUrl = 'https://restcountries.eu/rest/v2/name/$country';

String countryUrl = 'http://176.122.178.74:3000/foods';

// http

// .get(countryUrl)

// // .then((response) => jsonDecode(response.body)[0]['name'])

// .then((response) => jsonDecode(response.body))

// .then((decoded) => print(decoded))

// .catchError((error) => throw(error));

final response = await http.get('http://176.122.178.74:3000/foods');

// final jsonResponse = json.decode(response.body);

Map<String, dynamic> map = json.decode(response.body);

Map<String, dynamic> data = map["foods"];

for (final name in data.keys) {

final value = data[name];

print('$name,$value'); // prints entries like "AED,3.672940"

}

// Map<String, dynamic> data1 = data["icecream"];

// print(data1["name"]);

//List<dynamic> data1 = data["icecream"];

// final Map<String, dynamic> parsedmap = jsonDecode(jsonResponse);

// for(var u in jsonResponse){

// print(u);

// }

}

@override

Widget build(BuildContext context) {

return Scaffold(

body: Center(

child: MaterialButton(

onPressed: () => GetCountry('japan'),

child: Container(

color: Colors.blue,

padding: EdgeInsets.all(15),

child: Text('Get Country', style: TextStyle(color: Colors.white))),

);

}