Deep dive into Flutter App Lifecycle.

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Flutter is a popular open-source framework for building cross-platform applications. When building apps with Flutter, it’s important to understand the app lifecycle. The app lifecycle defines the various states that an app can be in and the methods that are called as the app transitions between those states. Understanding the app lifecycle can help us create more efficient and responsive apps.

In this blog, we’ll explore the Flutter app lifecycle and provide examples of how to handle the various app states.

So Let's deep dive into the Flutter app life cycle.

The Flutter App Lifecycle

The Flutter app lifecycle consists of four states:

1. resumed
2. inactive
3. paused
4. detached

Here’s a brief overview of each state:

• resumed: The app is in the foreground and is receiving user input.
• inactive: The app is in the foreground but is not receiving user input. This state can occur, for example, when a phone call comes in or when the user switches to another app.
• paused: The app is in the background and is not visible to the user. This state occurs when the user presses the home button or switches to another app.
• detached: The app is not running at all. This state can occur, for example, when the app is terminated by the operating system or when the device is restarted.

Handling App Lifecycle Events

Flutter provides several methods that are called app transitions between the different lifecycle states. These methods can be overridden to handle app lifecycle events. Here are the methods:

• didChangeAppLifecycleState: This method is called whenever the app transitions between lifecycle states. It receives an AppLifecycleState object that indicates the new state. You can use this method to perform actions when the app transitions between states.
• dispose: This method is called when the app is about to be destroyed. You can use this method to clean up any resources that your app is using.

Here are some examples of how to use these methods to handle app lifecycle events:

import 'package:flutter/material.dart';

class AppLifeCycleExample extends StatefulWidget {
  const AppLifeCycleExample({super.key});

  @override
  _AppLifeCycleExampleState createState() => _AppLifeCycleExampleState();
}

class _AppLifeCycleExampleState extends State<AppLifeCycleExample>
    with WidgetsBindingObserver {
  AppLifecycleState? _appLifecycleState;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);
    setState(() {
      _appLifecycleState = state;
      print(_appLifecycleState);
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('App Lifecycle Example'),
        ),
        body: Center(
          child: Text(
                  'App is currently in $_appLifecycleState state.',
                  textAlign: TextAlign.center,
                  style: const TextStyle(fontSize: 20),
                ),
        ),
      ),
    );
  }
}

In this example, we’re using the didChangeAppLifecycleState method to update the app's state and also print the state in the command line whenever the app transitions between lifecycle states. We're also using the dispose method to remove the observer that we added in the initState method.

UI Example

Command Line Example

Hurray! we have learned about the Flutter app lifecycle in a very simple way.

Conclusion

Understanding the Flutter app lifecycle is important for creating efficient and responsive apps. By using the methods provided by Flutter, you can handle app lifecycle events and perform actions when the app transitions between states. Remember to use the dispose method to clean up any resources that your app is using when it's about to be destroyed. With this knowledge, you'll be well-equipped to create great Flutter apps that provide a seamless user experience.

Thank you for reading this article, if you learned something new from this blog do clap as many times as possible, it really motivates me to share all my learnings with the flutter community.

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Image Credits: Image by storyset