When to Use ChangeNotifier in Dart Flutter App

In Flutter development with Android Studio, ChangeNotifier is a simple yet powerful way to implement state management without external packages. It’s part of the flutter/foundation library and works perfectly for small to medium applications where you need to notify listeners about data changes. But when exactly should you use ChangeNotifier instead of other state management techniques like Riverpod or Bloc?

You should consider ChangeNotifier when:

• Your app has simple state logic (e.g., toggle, counters, forms)
• You want built-in support without dependencies
• Performance is not heavily impacted by widget rebuilds
• You are building for learning or prototyping

Here’s a complete example using ChangeNotifier in an Android Studio Flutter project:

1. CounterModel Class with ChangeNotifier

import 'package:flutter/foundation.dart';

class CounterModel extends ChangeNotifier {
  int _count = 0;

  int get count => _count;

  void increment() {
    _count++;
    notifyListeners(); // notify widgets listening to this model
  }
}

2. Main App with ChangeNotifierProvider

import 'package:flutter/material.dart';
import 'package:provider/provider.dart'; // External link for Provider: https://pub.dev/packages/provider
import 'counter_model.dart';

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => CounterModel(),
      child: const MyApp(),
    ),
  );
}

3. MyApp and HomePage

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'ChangeNotifier Demo',
      home: const HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  const HomePage({super.key});

  @override
  Widget build(BuildContext context) {
    final counter = Provider.of<CounterModel>(context);

    return Scaffold(
      appBar: AppBar(title: const Text('Counter with ChangeNotifier')),
      body: Center(
        child: Text('Count: ${counter.count}', style: const TextStyle(fontSize: 24)),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: counter.increment,
        child: const Icon(Icons.add),
      ),
    );
  }
}

This code shows how ChangeNotifier can simplify state management for basic use cases. However, for more complex state logic or dependency injection, consider advanced solutions like Riverpod, Bloc, or GetX.