How to refresh FutureBuilder on button click in Flutter

In this Google flutter code example we are going to learn how to refresh FutureBuilder on button click in Flutter.

You can copy and adopt this source code example in your flutter project without reinventing the wheel.

The comments on the code provide more detailed explanation

The code is based on flutter version 1.

main.dart (App entry point)

import 'package:flutter/material.dart';
import 'refresh_futurebuilder.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: RefreshFutureBuilder(),
    );
  }
}

Add Dart Http Library

name: food_store
description: A new Flutter project.

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# Read more about versioning at semver.org.
version: 1.0.0+1

environment:
  sdk: ">=2.0.0-dev.68.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2
  http: 0.12.0
  dio: 2.0.22
 
  dev_dependencies:
  flutter_test:
    sdk: flutter

# For information on the generic Dart part of this file, see the
# following page: https://www.dartlang.org/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:
  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  assets:
    - assets/images/umbrella.png
    - assets/images/dnut.png
    - assets/star_anim.flr

  fonts:
    - family: AvenirNext
      fonts:
        - asset: assets/fonts/AvenirNextLTPro-Regular.otf

  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg
  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.io/assets-and-images/#resolution-aware.
  # For details regarding adding assets from package dependencies, see
  # https://flutter.io/assets-and-images/#from-packages
  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.io/custom-fonts/#from-packages

Create new Dart file in lib folder

Go to the lib folder and create a dart file. Name the file json_array.dart.

Import Flutter Firestore package and dart async also.

Open the newly created dart file and add the code below.

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

import 'package:flutter/material.dart';

class RefreshFutureBuilder extends StatefulWidget {
  @override
  _RefreshFutureBuilderState createState() => _RefreshFutureBuilderState();
}

class _RefreshFutureBuilderState extends State<RefreshFutureBuilder> {
  final String uri = 'https://jsonplaceholder.typicode.com/users';

  Future<List<Users>> users;

  @override
  void initState() {
    super.initState();
    users = _fetchUsers();
  }

  Future<List<Users>> _fetchUsers() async {
    var response = await http.get(uri);

    if (response.statusCode == 200) {
      final items = json.decode(response.body).cast<Map<String, dynamic>>();
      List<Users> listOfUsers = items.map<Users>((json) {
        return Users.fromJson(json);
      }).toList();

      return listOfUsers;
    } else {
      throw Exception('Failed to load internet');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Refresh FutureBuilder")),
      body: ListView(
        children: <Widget>[
          FutureBuilder<List<Users>>(
              future: users,
              builder:
                  (BuildContext context, AsyncSnapshot<List<Users>> snapshot) {
                if (!snapshot.hasData)
                  return Center(child: CircularProgressIndicator());

                return Column(
                  children: snapshot.data
                      .map((user) => ListTile(
                            title: Text(user.name),
                            subtitle: Text(user.email),
                          ))
                      .toList(),
                );
              }),
          SizedBox(height: 20.0),
          RaisedButton(
            child: Text("REFRESH"),
            color: Colors.red,
            onPressed: () {
              setState(() {
                users = _fetchUsers();
              });
            },
          )
        ],
      ),
    );
  }
}

class Users {
  int id;
  String name;
  String username;
  String email;

  Users({
    this.id,
    this.name,
    this.username,
    this.email,
  });

  factory Users.fromJson(Map<String, dynamic> json) {
    return Users(
      id: json['id'],
      name: json['name'],
      email: json['email'],
      username: json['username'],
    );
  }
}

RUN YOUR APP

You can use flutter command to run your app – $ flutter run

If everything goes well, you will see screen similar to the image below in your flutter device.

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