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Flutter – Updating Data on the Internet

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  • Last Updated : 21 Jun, 2022
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In today’s world, most applications heavily rely on fetching and updating 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 update the data on the Internet follow the below steps:

  1. Import the http package
  2. Update data t using the http package
  3. Convert the response into a custom Dart object
  4. Get the data from the internet.
  5. Update and display the response on the screen

Importing The http Package:

To install the http package use the below command in your command prompt:

pub get

Or, if you’re 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;

Update Data over the Internet:

Use the http.put() method to update the title of the Album in JSONPlaceholder as shown below:

Dart




Future<Album> updateAlbum(String title) async {
  final http.Response response = await http.put(
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
    body: jsonEncode(<String, String>{
      'title': title,
    }),
  );


Converting the Response:

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 id;
  final String title;
 
  Album({required this.id, required this.title});
 
  factory Album.fromJson(Map<String, dynamic> json) {
    return Album(
      id: json['id'],
      title: json['title'],
    );
  }
}


Convert http.Response to an Album:

Now, follow the below steps to update the fetchAlbum() function to return a Future<Album>:

  1. Use the dart: convert package to convert the response body into a JSON Map.
  2. Use the fromJSON() factory method to convert JSON Map into Album if the server returns an OK response with a status code of 200.
  3. Throw an exception if the server doesn’t return an OK response with a status code of 200.

Dart




Future<Album> updateAlbum(String title) async {
  final http.Response response = await http.put(
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
    body: jsonEncode(<String, String>{
      'title': title,
    }),
  );
// parsing JSOn or throwing an exception
  if (response.statusCode == 200) {
    return Album.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to update album.');
  }
}


Fetching the Data:

Now use the fetch() method to fetch the data as shown below:

Dart




Future<Album> fetchAlbum() async {
  final response = await http
      .get(Uri.parse('https://jsonplaceholder.typicode.com/albums/1'));
 
// Dispatch action depending upon
//the server response
  if (response.statusCode == 200) {
    return Album.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to load album');
  }
}


Update the existing Data through user input:

Now create a TextField for the user to enter a title and a RaisedButton to send data to the server. Also, define a TextEditingController to read the user input from a TextField as shown below:

Dart




Column(
    mainAxisAlignment: MainAxisAlignment.center,
    children: <Widget>[
      Text(snapshot.data!.title),
      TextField(
        controller: _controller,
        decoration:
            const InputDecoration(hintText: 'Enter Title'),
      ),
       
      ElevatedButton(
        child: const Text('Update Data'),
        onPressed: () {
          setState(() {
            _futureAlbum = updateAlbum(_controller.text);
          });
        },
      )


Displaying the Data:

Use the FlutterBuilder widget to display the data on the screen as shown below:

Dart




FutureBuilder<Album>(
   future: _futureAlbum,
   builder: (context, snapshot) {
     if (snapshot.connectionState == ConnectionState.done) {
       if (snapshot.hasData) {
         return Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
             Text(snapshot.data!.title),
             TextField(
               controller: _controller,
               decoration:
                   const InputDecoration(hintText: 'Enter Title'),
             ),
             ElevatedButton(
               child: const Text('Update Data'),
               onPressed: () {
                 setState(() {
                   _futureAlbum = updateAlbum(_controller.text);
                 });
               },
             )
 
             // RaisedButton is deprecated and should not be used.
             // Use ElevatedButton instead.
 
             // RaisedButton(
             //     child: const Text('Update Data'),
             //     onPressed: () {
             //     setState(() {
             //         _futureAlbum = updateAlbum(_controller.text);
             //     });
             //     },
             // ),
           ],
         );
       } else if (snapshot.hasError) {
         return Text("${snapshot.error}");
       }
     }
     return const 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(Uri.parse('https://jsonplaceholder.typicode.com/albums/1'));
 
// Dispatch action depending upon
//the server response
  if (response.statusCode == 200) {
    return Album.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to load album');
  }
}
 
Future<Album> updateAlbum(String title) async {
  final http.Response response = await http.put(
    headers: <String, String>{
      'Content-Type': 'application/json; charset=UTF-8',
    },
    body: jsonEncode(<String, String>{
      'title': title,
    }),
  );
// parsing JSOn or throwing an exception
  if (response.statusCode == 200) {
    return Album.fromJson(json.decode(response.body));
  } else {
    throw Exception('Failed to update album.');
  }
}
 
class Album {
  final int id;
  final String title;
 
  Album({required this.id, required this.title});
 
  factory Album.fromJson(Map<String, dynamic> json) {
    return Album(
      id: json['id'],
      title: json['title'],
    );
  }
}
 
void main() {
  runApp(const MyApp());
}
 
class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);
 
  @override
// ignore: library_private_types_in_public_api
  _MyAppState createState() {
    return _MyAppState();
  }
}
 
class _MyAppState extends State<MyApp> {
  final TextEditingController _controller = TextEditingController();
  late Future<Album> _futureAlbum;
 
  @override
  void initState() {
    super.initState();
    _futureAlbum = fetchAlbum();
  }
 
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Update Data Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: const Text('GeeksForGeeks'),
          backgroundColor: Colors.green,
        ),
        body: Container(
          alignment: Alignment.center,
          padding: const EdgeInsets.all(8.0),
          child: FutureBuilder<Album>(
            future: _futureAlbum,
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                if (snapshot.hasData) {
                  return Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Text(snapshot.data!.title),
                      TextField(
                        controller: _controller,
                        decoration:
                            const InputDecoration(hintText: 'Enter Title'),
                      ),
                      ElevatedButton(
                        child: const Text('Update Data'),
                        onPressed: () {
                          setState(() {
                            _futureAlbum = updateAlbum(_controller.text);
                          });
                        },
                      )
 
                      // RaisedButton is deprecated and should not be used.
                      // Use ElevatedButton instead.
 
                      // RaisedButton(
                      //     child: const Text('Update Data'),
                      //     onPressed: () {
                      //     setState(() {
                      //         _futureAlbum = updateAlbum(_controller.text);
                      //     });
                      //     },
                      // ),
                    ],
                  );
                } else if (snapshot.hasError) {
                  return Text("${snapshot.error}");
                }
              }
              return const CircularProgressIndicator();
            },
          ),
        ),
      ),
    );
  }
}


Output:


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