Flutter - Fetching Data From the Internet - GeeksforGeeks

14 Aug, 2021
In today’s world, most applications heavily rely on fetching information from the servers through the internet. In Flutter, such services are provided by the http package. In this article we will explore the same.
To fetch data from the internet follow the below steps:
Import the http packageMake a network request using the http packageConvert the response into custom Dart objectDisplay the data in a suitable format
Import the http package
Make a network request using the http package
Convert the response into custom Dart object
Display the data in a suitable format
To install the http package use the below command in your command prompt:
pub get
or, if you are using the flutter cmd use the below command:
flutter pub get
After the installation add the dependency to the pubsec.yml file as shown below:
import 'package:http/http.dart' as http;
We can use the http.get() method to fetch the sample album data from JSONPlaceholder as shown below:
Dart
Future<http.Response> fetchAlbum() {  return http.get('https://jsonplaceholder.typicode.com/albums/1');}
Though making a network request is no big deal, working with the raw response data can be inconvenient. To make your life easier, converting the raw data (ie, http.response) into dart object. Here we will create an Album class that contains the JSON data as shown below:
Dart
class Album {  final int userId;  final int id;  final String title;   Album({this.userId, this.id, this.title});   factory Album.fromJson(Map<String, dynamic> json) {    return Album(      userId: json['userId'],      id: json['id'],      title: json['title'],    );  }}
Now, follow the below steps to update the fetchAlbum() function to return a Future<Album>:
Use the dart: convert package to convert the response body into a JSON Map.Use the fromJSON() factory method to convert JSON Map into Album if the server returns an OK response with a status code of 200.Throw an exception if the server doesn’t return an OK response with a status code of 200.
Use the dart: convert package to convert the response body into a JSON Map.
Use the fromJSON() factory method to convert JSON Map into Album if the server returns an OK response with a status code of 200.
Throw an exception if the server doesn’t return an OK response with a status code of 200.
Dart
Future<Album> fetchAlbum() async {  final response = await http.get('https://jsonplaceholder.typicode.com/albums/1');   if (response.statusCode == 200) {    return Album.fromJson(json.decode(response.body));  } else {    throw Exception('Failed to load album');  }}
  
 
Now use the fetch() method to fetch the data as shown below:
 
Dart
class _MyAppState extends State<MyApp> {  Future<Album> futureAlbum;   @override  void initState() {    super.initState();    futureAlbum = fetchAlbum();  }
Use the FlutterBuilder widget to display the data on the screen as shown below:
Dart
FutureBuilder<Album>(  future: futureAlbum,  builder: (context, snapshot) {    if (snapshot.hasData) {      return Text(snapshot.data.title);    } else if (snapshot.hasError) {      return Text("${snapshot.error}");    }     // spinner    return CircularProgressIndicator();  },);
Complete Source Code:
Dart
import 'dart:async';import 'dart:convert'; import 'package:flutter/material.dart';import 'package:http/http.dart' as http; Future<Album> fetchAlbum() async {  final response =      await http.get('https://jsonplaceholder.typicode.com/albums/1');   // Appropriate action depending upon the  // server response  if (response.statusCode == 200) {    return Album.fromJson(json.decode(response.body));  } else {    throw Exception('Failed to load album');  }} class Album {  final int userId;  final int id;  final String title;   Album({this.userId, this.id, this.title});   factory Album.fromJson(Map<String, dynamic> json) {    return Album(      userId: json['userId'],      id: json['id'],      title: json['title'],    );  }} void main() => runApp(MyApp()); class MyApp extends StatefulWidget {  MyApp({Key key}) : super(key: key);   @override  _MyAppState createState() => _MyAppState();} class _MyAppState extends State<MyApp> {  Future<Album> futureAlbum;   @override  void initState() {    super.initState();    futureAlbum = fetchAlbum();  }   @override  Widget build(BuildContext context) {    return MaterialApp(      title: 'Fetching Data',      theme: ThemeData(        primarySwatch: Colors.blue,      ),      home: Scaffold(        appBar: AppBar(          title: Text('GeeksForGeeks'),        ),        body: Center(          child: FutureBuilder<Album>(            future: futureAlbum,            builder: (context, snapshot) {              if (snapshot.hasData) {                return Text(snapshot.data.title);              } else if (snapshot.hasError) {                return Text("${snapshot.error}");              }              return CircularProgressIndicator();            },          ),        ),      ),    );  }}
Output:
sumitgumber28
android
Flutter
Dart
Flutter
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