Getting data from Json in Flutter - json

Question

I'm a very beginner at Flutter development, in the code below I tried to get data from here and display it in ListView :
static final String URL = "https://corona.lmao.ninja/countries";
Future<List<CoronaModel>> getData() async {
var data = await http.get(URL);
var jsonData = json.decode(data.body);
print("the count is: " + jsonData.toString()); //Data successfully printed
List<CoronaModel> listCoronaCountries = [];
for (var item in jsonData) {
CoronaModel mCorona = CoronaModel(
item["country"],
item["recovered"],
item["cases"],
item["critical"],
item["deaths"],
item["todayCases"],
item["todayDeaths"]);
listCoronaCountries.add(mCorona);
}
if (listCoronaCountries.length > 0) {
print("the count is: " + listCoronaCountries.length.toString());
} else {
print("EMPTY");
}
return listCoronaCountries;
}
At run time, the first print works, I can see the data successfully printed, but the IF statement is not showing
if (listCoronaCountries.length > 0) {
print("the count is: " + listCoronaCountries.length.toString());
} else {
print("EMPTY");
}
Model :
class CoronaModel {
final String country;
final String recovered;
final String cases;
final String critical;
final String deaths;
final String todayCases;
final String todayDeaths;
CoronaModel(this.country, this.recovered, this.cases, this.critical,
this.deaths, this.todayCases, this.todayDeaths);
}

Answer 1

You can copy paste run full code below
You can parse with coronaModelFromJson and display with FutureBuilder
code snippet
List<CoronaModel> coronaModelFromJson(String str) => List<CoronaModel>.from(
json.decode(str).map((x) => CoronaModel.fromJson(x)));
Future<List<CoronaModel>> getData() async {
var data = await http.get(URL);
List<CoronaModel> listCoronaCountries = coronaModelFromJson(data.body);
return listCoronaCountries;
}
working demo
full code
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
// To parse this JSON data, do
//
// final coronaModel = coronaModelFromJson(jsonString);
import 'dart:convert';
List<CoronaModel> coronaModelFromJson(String str) => List<CoronaModel>.from(
json.decode(str).map((x) => CoronaModel.fromJson(x)));
String coronaModelToJson(List<CoronaModel> data) =>
json.encode(List<dynamic>.from(data.map((x) => x.toJson())));
class CoronaModel {
String country;
int cases;
int todayCases;
int deaths;
int todayDeaths;
int recovered;
int active;
int critical;
int casesPerOneMillion;
CoronaModel({
this.country,
this.cases,
this.todayCases,
this.deaths,
this.todayDeaths,
this.recovered,
this.active,
this.critical,
this.casesPerOneMillion,
});
factory CoronaModel.fromJson(Map<String, dynamic> json) => CoronaModel(
country: json["country"],
cases: json["cases"],
todayCases: json["todayCases"],
deaths: json["deaths"],
todayDeaths: json["todayDeaths"],
recovered: json["recovered"],
active: json["active"],
critical: json["critical"],
casesPerOneMillion: json["casesPerOneMillion"],
);
Map<String, dynamic> toJson() => {
"country": country,
"cases": cases,
"todayCases": todayCases,
"deaths": deaths,
"todayDeaths": todayDeaths,
"recovered": recovered,
"active": active,
"critical": critical,
"casesPerOneMillion": casesPerOneMillion,
};
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
static final String URL = "https://corona.lmao.ninja/countries";
Future _future;
Future<List<CoronaModel>> getData() async {
var data = await http.get(URL);
List<CoronaModel> listCoronaCountries = coronaModelFromJson(data.body);
return listCoronaCountries;
}
#override
void initState() {
// TODO: implement initState
super.initState();
_future = getData();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: FutureBuilder<List<CoronaModel>>(
future: _future,
builder: (BuildContext context,
AsyncSnapshot<List<CoronaModel>> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('Input a URL to start');
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.active:
return Text('');
case ConnectionState.done:
if (snapshot.hasError) {
return Text(
'${snapshot.error}',
style: TextStyle(color: Colors.red),
);
} else {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(
' ${snapshot.data[index].country} , ${snapshot.data[index].cases}'),
);
});
}
}
}));
}
}

Answer 2

Instead of hand coding '.fromJson/.toJson' methods. you could rely on
this library https://github.com/k-paxian/dart-json-mapper,
It will help you not only for this case, but for all Dart Object => JSON => Dart Object cases.