Flutter: Navigation, Networking & Platform

Navigation (GoRouter — recommended)

// pubspec.yaml: go_router: ^13.0.0

final router = GoRouter(
  initialLocation: '/',
  routes: [
    GoRoute(path: '/', builder: (context, state) => const HomeScreen()),
    GoRoute(
      path: '/users/:id',
      builder: (context, state) {
        final id = state.pathParameters['id']!;
        return UserDetailScreen(userId: id);
      },
    ),
    ShellRoute(
      builder: (context, state, child) => AppShell(child: child),
      routes: [
        GoRoute(path: '/feed',    builder: (_, __) => const FeedScreen()),
        GoRoute(path: '/profile', builder: (_, __) => const ProfileScreen()),
      ],
    ),
  ],
  redirect: (context, state) {
    final isLoggedIn = ref.read(authProvider).isAuthenticated;
    if (!isLoggedIn && state.matchedLocation != '/login') return '/login';
    return null;
  },
);

// Navigate
context.go('/users/123')           // replace current
context.push('/users/123')         // push onto stack
context.pop()                      // go back
context.goNamed('userDetail', pathParameters: {'id': '123'})

HTTP & Networking

// pubspec.yaml: http: ^1.2.0   (or dio: ^5.4.0 for interceptors)

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

class ApiService {
  static const _baseUrl = 'https://api.example.com';
  final String _token;

  ApiService(this._token);

  Future<User> getUser(String id) async {
    final response = await http.get(
      Uri.parse('$_baseUrl/users/$id'),
      headers: {'Authorization': 'Bearer $_token', 'Content-Type': 'application/json'},
    );

    if (response.statusCode == 200) {
      return User.fromJson(jsonDecode(response.body));
    } else if (response.statusCode == 404) {
      throw UserNotFoundException(id);
    } else {
      throw ApiException(response.statusCode, response.body);
    }
  }

  Future<User> createUser(CreateUserDto dto) async {
    final response = await http.post(
      Uri.parse('$_baseUrl/users'),
      headers: {'Authorization': 'Bearer $_token', 'Content-Type': 'application/json'},
      body: jsonEncode(dto.toJson()),
    );
    return User.fromJson(jsonDecode(response.body));
  }
}

// JSON serialization with freezed/json_serializable
// pubspec.yaml: freezed_annotation, json_annotation, build_runner, freezed, json_serializable

@freezed
class User with _$User {
  const factory User({
    required String id,
    required String name,
    required String email,
  }) = _User;

  factory User.fromJson(Map<String, dynamic> json) => _$UserFromJson(json);
}

Platform Channels & Plugins

• Platform channels: bidirectional communication between Dart and native (iOS/Android) code

• pub.dev: official package repository — search before writing native code

• Popular plugins: camera, geolocator, local_notifications, shared_preferences, sqflite (SQLite), firebase_core, in_app_purchase

• shared_preferences: key-value storage (UserDefaults on iOS, SharedPreferences on Android)

• sqflite: SQLite for Flutter — local structured data storage

• firebase_core + firebase_auth + cloud_firestore: Firebase integration

// shared_preferences — persistent key-value storage
import 'package:shared_preferences/shared_preferences.dart';

final prefs = await SharedPreferences.getInstance();
await prefs.setString('token', token);
final token = prefs.getString('token');
await prefs.remove('token');

// Platform channel (calling native code)
const _channel = MethodChannel('com.example.myapp/biometric');

Future<bool> authenticateWithBiometric() async {
  try {
    return await _channel.invokeMethod<bool>('authenticate') ?? false;
  } on PlatformException catch (e) {
    print('Biometric failed: ${e.message}');
    return false;
  }
}