Flutter Course, Definition of Status 4.4

Flutter Tutorial 4.4 Definition of State

Flutter is Google’s UI toolkit that helps developers quickly and easily build applications for multiple platforms, including iOS, Android, the web, and desktop. Especially, Flutter’s state management is an important concept that supports developers in effectively handling changes in the UI. In this tutorial, we will take an in-depth look at the definition of ‘state’ and how it applies to Flutter applications.

What is State?

In software development, state is a set of data that represents the current status of an application or object. The state can change due to user actions, application behavior, responses from external APIs, and various other factors. This state generally contains the information necessary to render a specific UI of the application.

State Management in Flutter

In Flutter, state management encompasses various techniques and patterns that help the UI of an application react to data changes. State management can primarily be divided into two categories:

  • Local State: A state that is used only within a widget, which the widget owns. For instance, whether a button has been clicked or the value entered in a text field falls under this category.
  • Global State: A state accessible throughout the application, which contains information shared across multiple widgets. This includes user authentication states or the list of items in a shopping cart.

Lifecycle of State

In Flutter, state has the following lifecycle:

  1. Create: The state is initially created. Initialization tasks may be needed at this point.
  2. Update: When the state information changes, the widgets using that state are re-rendered.
  3. Dispose: States that are no longer needed are released. Resource management may be necessary in this process.

Key Patterns for State Management

Various state management patterns are used in Flutter. The main patterns include:

  • setState: The most basic state management method that uses StatefulWidget to manage state. It is suitable for simple use cases but can be hard to manage in complex applications.
  • InheritedWidget: A method that allows data to propagate through the widget tree, enabling nested widgets to access the state of their parent widget.
  • Provider Pattern: A package that makes state management more convenient based on InheritedWidget. It is suitable for global state management.
  • BLoC (Business Logic Component): A pattern that separates business logic from the UI, managing state through streams and data flow. It is useful for managing communication with external data, such as REST APIs.
  • Riverpod: A pattern that improves on Provider’s drawbacks, offering more flexibility and simplicity. It features type safety and ease of testing.

State Management Practice: Creating a Simple Counter Application

Let’s practice the basics of state management in Flutter. We will learn the state management method using setState by creating a simple counter app.

1. Create a Project

First, create a Flutter project. Use the following command:

flutter create counter_app

2. Add Counter Logic

Add the following code in the lib/main.dart file:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: CounterPage(),
    );
  }
}

class CounterPage extends StatefulWidget {
  @override
  _CounterPageState createState() => _CounterPageState();
}

class _CounterPageState extends State {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Counter App'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              'Button pressed:',
            ),
            Text(
              '$_counter',
              style: TextStyle(fontSize: 50),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

3. Run the Application

When you run the app, you will see a simple UI with a button that increases the count. Each time the button is pressed, setState is called to update the UI.

State Management Tools and Packages

There are various state management tools and packages in the Flutter ecosystem. Some of them include:

  • Provider: A package that helps easily share state between different widgets.
  • Riverpod: An upgraded package of Provider that offers more powerful state management.
  • BLoC: A pattern that allows state management using data streams.
  • GetX: A package that supports lightweight state management, routing, and dependency injection.

Conclusion

The concept of state management in Flutter is essential to understanding the relationship between an application’s behavior and its UI. Through various tools and patterns, developers can efficiently manage complex states and improve user experience. I hope this tutorial provides a foundation for understanding Flutter’s state management and helps you develop better applications.