Persisting Data in Your Flutter App with SharedPreferences

What is SharedPreferences in Flutter?

SharedPreferences is a mechanism used by Android and iOS apps to store simple data in an allocated space. This data persists even when the app is shut down and starts up again, allowing you to retrieve the value as it was. The data stored in SharedPreferences can be edited and deleted, and is stored in a key-value pair.

Scaffolding a Flutter Project

To get started, you’ll need to have the Flutter SDK and a code editor installed on your machine. Once you’ve set up your development environment, you can scaffold a new Flutter project using the following command:

flutter create shared_pref

This command creates a new folder called shared_pref and generates a basic Flutter project inside it.

Installing the shared_preferences Plugin

To use SharedPreferences in your Flutter app, you’ll need to install the shared_preferences plugin. Open the pubspec.yaml file and add the following dependency:

dependencies:
  flutter:
    sdk: flutter
  shared_preferences: ^2.0.3

Then, import the plugin into your Dart file:

import 'package:shared_preferences/shared_preferences.dart';

Using SharedPreferences in Your Flutter App

The shared_preferences plugin provides several methods for working with SharedPreferences, including:

• getInstance
• getInt
• getString
• getBool
• getDouble
• remove
• containsKey

Here’s an example of how to add data to SharedPreferences:

Future<void> _addData() async {
  final prefs = await SharedPreferences.getInstance();
  prefs.setInt('counter', 1);
  prefs.setString('message', 'Hello, World!');
  prefs.setBool('isAdmin', true);
  prefs.setDouble('latitude', 37.7749);
}

And here’s an example of how to retrieve data from SharedPreferences:

Future<void> _retrieveData() async {
  final prefs = await SharedPreferences.getInstance();
  final counter = prefs.getInt('counter');
  final message = prefs.getString('message');
  final isAdmin = prefs.getBool('isAdmin');
  final latitude = prefs.getDouble('latitude');
}

Implementing a Splash Screen with SharedPreferences

You can also use SharedPreferences to implement a splash screen in your Flutter app. Here’s an example of how to do it:

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _newLaunch = true;

  @override
  void initState() {
    super.initState();
    _loadNewLaunch();
  }

  Future _loadNewLaunch() async {
    final prefs = await SharedPreferences.getInstance();
    setState(() {
      _newLaunch = prefs.getBool('newLaunch')?? true;
    });
  }

  @override
  Widget build(BuildContext context) {
    return _newLaunch
       ? SplashScreen()
        : ProfileScreen();
  }
}

In this example, we’re using SharedPreferences to store a boolean value called newLaunch. If the value is true, we show the splash screen. If the value is false, we show the profile screen.

Testing Your Flutter App

To test your Flutter app, run the following command:

flutter run

This will launch your app on an emulator or physical device. You can then interact with your app to see how the SharedPreferences data is persisted.

By using SharedPreferences in your Flutter app, you can provide a better user experience by storing and retrieving data locally. Whether you’re building a simple todo list app or a complex enterprise app, SharedPreferences is a powerful tool that can help you achieve your goals.