State Management in Flutter Apps — An Overview
Managing the state of an application is one of the most important and necessary processes in the life cycle of an application. With Flutter’s architecture, managing the state of your application becomes even more important.
In almost all apps, there is the concept of application state. every real-world app needs to handle its status at some point. As developers, we might start with one screen, but soon multiple screens with different features. These new screens might need to know what’s happening in the app. For example, in a shopping app, the cart screen should show what you picked from the catalog on the previous screen.
In Flutter, where everything is a ‘widget,’ things can get complex quickly. The widgets in these widget trees might need to share how the app is doing and pass this on to other widgets. So, it’s important to handle this widget-sharing thing or ‘State Management’ well. If not done right, the app could have problems when it grows.
When we talk about Flutter, the ways we structure the code and manage the state kind of mean the same thing. But using good code structure helps keep things organized.
The state is when a widget is active and stores its data in memory. Flutter divides app states into two types: ‘Ephemeral (local) State’ and ‘Application State.’
- Ephemeral (local) state is about one widget when no other component in the widget tree needs to access a widget’s data—for example when a tab is selected in
BottomNavigationBar - Application state is about the whole app, for example when the user selects and adds an item to a shopping cart.
You can learn more about different types of states on Flutter’s official page.
There are many ways to manage the app’s states in Flutter:
StatefulWidget
The most basic form of state management in Flutter is using the StatefulWidget class. This allows you to create a widget that has a mutable state. By extending StatefulWidget and implementing the associated State class, you can manage and update the state of your widget. This approach is suitable for simple applications or widgets that have their own isolated state.
Below is a basic case of ephemeral state management using StatefulWidget
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: CounterApp(),
);
}
}
class CounterApp extends StatefulWidget {
@override
_CounterAppState createState() => _CounterAppState();
}
class _CounterAppState extends State<CounterApp> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Ephemeral State Example'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Counter value:',
),
Text(
'$_counter',
style: TextStyle(fontSize: 36),
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}In this case, the _counter is the local or ephemeral state. It's managed within the _CounterAppState class, which is a State object associated with the CounterApp widget. The _incrementCounter function updates the _counter state when the FloatingActionButton is pressed. The setState method is used to notify Flutter that the state has changed, and the UI needs to be rebuilt.
For more complex scenarios and larger applications, you might want to explore state management solutions like Provider, Bloc, or Riverpod.
Provider
Provider is a popular state management library in Flutter that makes it easy to manage and share state across your application. It follows the InheritedWidget pattern to propagate the state down the widget tree. Provider is known for its simplicity and flexibility, allowing you to easily update and access state from anywhere in your app.
BLoC (Business Logic Component)
BLoC is another popular state management pattern in Flutter. It separates the business logic from the UI, making your code more maintainable and testable. BLoC relies on streams and sinks to handle the flow of data. It provides a clear separation between the UI layer and the business logic layer, making it suitable for managing complex app state.
Riverpod
Riverpod is a modern state management library for Flutter, built on top of Provider. It offers a more intuitive and declarative way to manage state in your Flutter applications. Riverpod embraces the concept of “providers,” which are used to expose and consume state in your app. It provides a flexible and efficient way to manage both local and app (global) state.
Redux
Redux is a predictable state container for Flutter applications. It is based on the Redux pattern, which separates the state from the UI and provides a unidirectional data flow. Redux is known for its strict immutability and pure functions, making it easier to reason about the state changes in your app. It is suitable for large-scale applications that require a robust state management solution.
In addition to these approaches, there are many other state management solutions available for Flutter, such as MobX and GetX. The best approach to state management will depend on the specific needs of your app, but the key is to carefully consider the trade-offs between simplicity, scalability, and performance when selecting a solution.
Overall, effective state management is critical to building high-quality Flutter apps. By selecting an appropriate state management approach and carefully managing the app state, developers can ensure that their apps function correctly and efficiently.
Conclusion
State management is a crucial aspect of building applications in Flutter. Depending on the complexity and scale of your app, you can choose from various state management techniques and libraries. Whether it’s managing local state within a widget or handling global state across your app, Flutter provides a range of options to suit your needs. Experiment with different approaches and choose the one that best fits your application’s requirements. Happy coding!
