Dart/Flutter JSON 解析和显示

Question

Dart / Flutter JSON parsing and display

I am having trouble parsing and displaying the info. Am getting data from API

I get a response == 200 from API but am unable to display it.

The printout on screen is "Instance of medData"

Future<medData> fetchData(http.Client client) async {
  final response = await http.get(
    'xxxxxxxxxx',
    headers: {
      "host": "rapidapi.com",
      "key": "x87439756734",
    },
  );

  if (response.statusCode == 200) {
    // List json = json.decode(response.body);
    // return json.map((medData) => new medData.fromJson(medData)).toList();
    return medData.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to load data from API');
  }
}

This Is the List View Builder

ListView _medDataListView(data) {
  return ListView.builder(
      itemCount: data.length,
      itemBuilder: (context, index) {
        return _tile(data[index].cases, data[index].number, Icons.work);
      });
}

Tile builder

ListTile _tile(String title, String subtitle, IconData icon) => ListTile(
      title: Text(title,
          style: TextStyle(
            fontWeight: FontWeight.w500,
            fontSize: 20,
          )),
      subtitle: Text(subtitle),
      leading: Icon(
        icon,
        color: Colors.blue[500],
      ),
    );

Class medData for parsing the JSON

class medData {
  String country;
  List<LatestStatByCountry> latestStatByCountry;

  medData({this.country, this.latestStatByCountry});

  medData.fromJson(Map<String, dynamic> json) {
    country = json['country'];
    if (json['latest_stat_by_country'] != null) {
      latestStatByCountry = new List<LatestStatByCountry>();
      json['latest_stat_by_country'].forEach((v) {
        latestStatByCountry.add(new LatestStatByCountry.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['country'] = this.country;
    if (this.latestStatByCountry != null) {
      data['latest_stat_by_country'] =
          this.latestStatByCountry.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class LatestStatByCountry {
  String id;
  String countryName;
  String totalCases;
  String newCases;
  String activeCases;
  String totalDeaths;
  String newDeaths;
  String totalRecovered;
  String seriousCritical;
  Null region;
  String totalCasesPer1m;
  String recordDate;

  LatestStatByCountry(
      {this.id,
      this.countryName,
      this.totalCases,
      this.newCases,
      this.activeCases,
      this.totalDeaths,
      this.newDeaths,
      this.totalRecovered,
      this.seriousCritical,
      this.region,
      this.totalCasesPer1m,
      this.recordDate});

  LatestStatByCountry.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    countryName = json['country_name'];
    totalCases = json['total_cases'];
    newCases = json['new_cases'];
    activeCases = json['active_cases'];
    totalDeaths = json['total_deaths'];
    newDeaths = json['new_deaths'];
    totalRecovered = json['total_recovered'];
    seriousCritical = json['serious_critical'];
    region = json['region'];
    totalCasesPer1m = json['total_cases_per1m'];
    recordDate = json['record_date'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['country_name'] = this.countryName;
    data['total_cases'] = this.totalCases;
    data['new_cases'] = this.newCases;
    data['active_cases'] = this.activeCases;
    data['total_deaths'] = this.totalDeaths;
    data['new_deaths'] = this.newDeaths;
    data['total_recovered'] = this.totalRecovered;
    data['serious_critical'] = this.seriousCritical;
    data['region'] = this.region;
    data['total_cases_per1m'] = this.totalCasesPer1m;
    data['record_date'] = this.recordDate;
    return data;
  }
}

Building the widget

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: FutureBuilder<medData>(
          future: fetchData(http.Client()),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              return Text("${snapshot.data}");
            } else if (snapshot.hasError) {
              return Text("${snapshot.error}");
            }
            return CircularProgressIndicator();
          },
        ),
      ),
    );
  }
} 

I don't really know what i'm doing wrong when trying to display the data.

Answer 1

You can copy paste run full code below
Step 1 : parse json string with medDataFromJson(response.body);

factory MedData.fromJson(Map<String, dynamic> json) => MedData(
        country: json["country"],
        latestStatByCountry: List<LatestStatByCountry>.from(
            json["latest_stat_by_country"]
                .map((x) => LatestStatByCountry.fromJson(x))),
      );

Step 2 : In FutureBuilder do return _medDataListView(snapshot.data.latestStatByCountry);

Step 3: ListView _medDataListView(List<LatestStatByCountry> data) data is List<LatestStatByCountry>

working demo

full code

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

// To parse this JSON data, do
//
//     final medData = medDataFromJson(jsonString);

import 'dart:convert';

MedData medDataFromJson(String str) => MedData.fromJson(json.decode(str));

String medDataToJson(MedData data) => json.encode(data.toJson());

class MedData {
  String country;
  List<LatestStatByCountry> latestStatByCountry;

  MedData({
    this.country,
    this.latestStatByCountry,
  });

  factory MedData.fromJson(Map<String, dynamic> json) => MedData(
        country: json["country"],
        latestStatByCountry: List<LatestStatByCountry>.from(
            json["latest_stat_by_country"]
                .map((x) => LatestStatByCountry.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "country": country,
        "latest_stat_by_country":
            List<dynamic>.from(latestStatByCountry.map((x) => x.toJson())),
      };
}

class LatestStatByCountry {
  String id;
  String countryName;
  String totalCases;
  String newCases;
  String activeCases;
  String totalDeaths;
  String newDeaths;
  String totalRecovered;
  String seriousCritical;
  dynamic region;
  String totalCasesPer1M;
  DateTime recordDate;

  LatestStatByCountry({
    this.id,
    this.countryName,
    this.totalCases,
    this.newCases,
    this.activeCases,
    this.totalDeaths,
    this.newDeaths,
    this.totalRecovered,
    this.seriousCritical,
    this.region,
    this.totalCasesPer1M,
    this.recordDate,
  });

  factory LatestStatByCountry.fromJson(Map<String, dynamic> json) =>
      LatestStatByCountry(
        id: json["id"],
        countryName: json["country_name"],
        totalCases: json["total_cases"],
        newCases: json["new_cases"],
        activeCases: json["active_cases"],
        totalDeaths: json["total_deaths"],
        newDeaths: json["new_deaths"],
        totalRecovered: json["total_recovered"],
        seriousCritical: json["serious_critical"],
        region: json["region"],
        totalCasesPer1M: json["total_cases_per1m"],
        recordDate: DateTime.parse(json["record_date"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "country_name": countryName,
        "total_cases": totalCases,
        "new_cases": newCases,
        "active_cases": activeCases,
        "total_deaths": totalDeaths,
        "new_deaths": newDeaths,
        "total_recovered": totalRecovered,
        "serious_critical": seriousCritical,
        "region": region,
        "total_cases_per1m": totalCasesPer1M,
        "record_date": recordDate.toIso8601String(),
      };
}

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'),
    );
  }
}

MedData medData;

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  ListView _medDataListView(List<LatestStatByCountry> data) {
    return ListView.builder(
        itemCount: data.length,
        itemBuilder: (context, index) {
          return _tile(
              data[index].countryName, data[index].totalCases, Icons.work);
        });
  }

  ListTile _tile(String title, String subtitle, IconData icon) => ListTile(
        title: Text(title,
            style: TextStyle(
              fontWeight: FontWeight.w500,
              fontSize: 20,
            )),
        subtitle: Text(subtitle),
        leading: Icon(
          icon,
          color: Colors.blue[500],
        ),
      );

  Future<MedData> fetchData(http.Client client) async {
    final response = await http.get(
      'https://coronavirus-monitor.p.rapidapi.com/coronavirus/latest_stat_by_country.php?country=South%20Africa',
      headers: {
        "x-rapidapi-host": "coronavirus-monitor.p.rapidapi.com",
        "x-rapidapi-key": "23bdb74dbfmsh865510b645e32f6p1f7b7bjsn2e800c1ac844",
      },
    );
    /*String jsonString = '''
    { "country": "South Africa", "latest_stat_by_country": [ { "id": "216413", "country_name": "South Africa", "total_cases": "709", "new_cases": "", "active_cases": "697", "total_deaths": "", "new_deaths": "", "total_recovered": "12", "serious_critical": "2", "region": null, "total_cases_per1m": "12", "record_date": "2020-03-26 05:50:02.171" } ] }
    ''';

    http.Response response = http.Response(jsonString, 200);*/
    if (response.statusCode == 200) {
      // List json = json.decode(response.body);
      // return json.map((medData) => new medData.fromJson(medData)).toList();
      //return medData.fromJson(json.decode(response.body));
      medData = medDataFromJson(response.body);
      return medData;
    } else {
      throw Exception('Failed to load data from API');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: FutureBuilder<MedData>(
          future: fetchData(http.Client()),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              //return Text("${snapshot.data}");
              return _medDataListView(snapshot.data.latestStatByCountry);
            } else if (snapshot.hasError) {
              return Text("${snapshot.error}");
            }
            return CircularProgressIndicator();
          },
        ),
      ),
    );
  }
}