Flutter API Integration with http – A Beginner's Guide

In Flutter, APIs allow your app to communicate with web services — such as fetching user data, posting forms, or connecting to any backend. In this tutorial, we’ll learn how to integrate REST APIs in Flutter using the http package, in a way that’s simple, clear, and production-ready.

What is an API?

An API (Application Programming Interface) is a way for your app to communicate with a backend server. It lets your app send and receive data.

for eg:

=> Your app asks: “Hey server, give me a list of users.”

=> The server replies with data like:

[
  {
    "id": 1,
    "name": "John Doe",
    "email": "john@example.com"
  }
]

=> look at the free api given below, copy and paste it to your browser and see the result :

https://jsonplaceholder.typicode.com/users

returns a list of fake users in JSON format. We can display that data in our Flutter app.

That’s a GET request. You can also use POST to send data, PUT to update, and DELETE to remove items.

Before Moving into the project make a project structure:

lib/
├── user_model.dart
├── api_service.dart
└── user_list_screen.dart

Step 1: Add http Package

Flutter doesn’t come with built-in tools for making HTTP requests, so we use the http package.

Open Your Terminal and run

flutter pub add http

Learn More : https://pub.dev/packages/http

Step 2: Create a User Model

APIs return data in JSON format (i.e., a structured string of key-value pairs). We convert that JSON into Dart objects using a model class.

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Here’s an example JSON from the API:

{
  "id": 1,
  "name": "Leanne Graham",
  "email": "Sincere@april.biz"
}

First, we need a model class to parse the JSON response from the API into Dart objects:

class User {
  final int id;
  final String name;
  final String email;

  User({required this.id, required this.name, required this.email});

  // Converts JSON map to User object
  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json['id'],
      name: json['name'],
      email: json['email'],
    );
  }
}

• factory User.fromJson(...) is a constructor that creates a User from a map (parsed JSON).
• required ensures null-safety, so all fields must be provided.

Step 3: Write an API Service

This is a class responsible for sending requests and returning parsed data.

Let’s build a service class that uses the http package to fetch users:

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

class ApiService {
  final String url = 'https://jsonplaceholder.typicode.com/users';

  Future<List<User>> fetchUsers() async {
    final response = await http.get(Uri.parse(url));

    if (response.statusCode == 200) {
      // Convert JSON response to List<dynamic>
      List<dynamic> body = jsonDecode(response.body);
      
      // Map each item to a User object
      List<User> users = body.map((e) => User.fromJson(e)).toList();
      
      return users;
    } else {
      throw Exception('Failed to load users');
    }
  }
}

• http.get(Uri.parse(url)): Sends a GET request to the URL.
• jsonDecode(response.body): Converts JSON string into a Dart object.
• List<dynamic>: Represents the JSON array of users.
• .map((e) => User.fromJson(e)).toList(): Converts each JSON map to a User

Step 4: Display API Data in the UI

This is a class responsible for sending requests and returning parsed data.

Let’s now use FutureBuilder to display the fetched data in a widget:

import 'package:flutter/material.dart';
import 'user_model.dart';
import 'api_service.dart';

class UserListScreen extends StatefulWidget {
  @override
  _UserListScreenState createState() => _UserListScreenState();
}

class _UserListScreenState extends State<UserListScreen> {
  late Future<List<User>> futureUsers;

  @override
  void initState() {
    super.initState();
    futureUsers = ApiService().fetchUsers(); // fetch data once on start
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Users')),
      body: FutureBuilder<List<User>>(
        future: futureUsers,
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting)
            return Center(child: CircularProgressIndicator());
          else if (snapshot.hasError)
            return Center(child: Text('Error: ${snapshot.error}'));
          else if (!snapshot.hasData || snapshot.data!.isEmpty)
            return Center(child: Text('No users found.'));
          else {
            return ListView.builder(
              itemCount: snapshot.data!.length,
              itemBuilder: (_, index) {
                final user = snapshot.data![index];
                return ListTile(
                  title: Text(user.name),
                  subtitle: Text(user.email),
                );
              },
            );
          }
        },
      ),
    );
  }
}

What We Have Learnt

=> Add and use the http package

=> Fetch data from a REST API

=> Convert JSON to Dart models

=> Display it with FutureBuilder