flutter_cache

A: the preface

Some data is often used in the project development (such as account number, token, etc.), and also want to open the app data is still there, all this time you can put some data stored in cache, next time can be obtained directly from the cache, whereby encapsulate a cache class or very be necessary, individual packaging ideas are as follows:

• Encapsulate a cache class with a singleton, initialize it in the main function, and add some common methods to the class

• Encapsulate a utility class to hold commonly used key names

• Yjf -ll/flutter_cache (github.com)

Two: Without further ado, let’s begin

• To add a cache dependency library to your project, I’m using shared_Preferences

  flutter pub add shared_preferences

• Write the cache key name utility class

  // The key name of the value in the cache. The format varies from person to project
  class CacheKey {
    static const String TOKEN = 'app_token';
  
    static const String PHONE = 'app_phone';
  }
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• Writing a cache class

  class AppCache {
    final SharedPreferences sharedPreferences;
  
    AppCache._({required this.sharedPreferences});
  
    factory AppCache.create({
      required SharedPreferences sharedPreferences,
    }) =>
        AppCache._(
          sharedPreferences: sharedPreferences,
        );
  
    // The cache class takes the singleton pattern
    static AppCache? _instance;
  
    // It must be initialized in main
    static Future<void> init() async{ _instance ?? = AppCache.create( sharedPreferences:await SharedPreferences.getInstance(),
      );
    }
  
    // Simplify the retrieval of cached instances of utility classes to encapsulate some methods below
    static SharedPreferences get_pre => _instance! .sharedPreferences;// Encapsulate the method to set the token
    static Future<bool> setToken(String token) async {
      return await _pre.setString(CacheKey.TOKEN, token);
    }
  
    // Encapsulate the token clearing method
    static Future<bool> cleanToken() async {
      return await _pre.setString(CacheKey.TOKEN, ' ');
    }
  
    // Encapsulate the method to obtain the token
    static String? get token => _pre.getString(CacheKey.TOKEN);
  
    // Encapsulate the method for setting phone
    static Future<bool> setPhone(String phone) async {
      return _pre.setString(CacheKey.PHONE, phone);
    }
  
    // Encapsulate the method to clear phone
    static Future<bool> cleanPhone() async {
      return await _pre.setString(CacheKey.PHONE, ' ');
    }
  
    // Encapsulate the method to get the phone
    static String? get phone => _pre.getString(CacheKey.PHONE);
  
  }
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• The home page code is as follows

  Future<void> main() async {
    // If you don't want to use this command, you'll get an error
    WidgetsFlutterBinding.ensureInitialized();
    // Initialize the cache utility class
    await AppCache.init();
    runApp(MyApp());
  }
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      returnMaterialApp( theme: ThemeData( primarySwatch: Colors.blue, ), home: HomePage(), ); }}class HomePage extends StatefulWidget {
    const HomePage({Key? key}) : super(key: key);
  
    @override
    _HomePageState createState() => _HomePageState();
  }
  
  class _HomePageState extends State<HomePage> {
    String? phone;
  
    @override
    void didChangeDependencies() {
      super.didChangeDependencies();
      getPhone();
    }
  
    void getPhone() {
      print('Get mobile phone number');
      setState(() {
        // Get the data you want by calling some of the get methods set by the utility class
        phone = AppCache.phone;
      });
    }
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text('Cache demo'),
          centerTitle: true,
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text('The current saved mobile phone number is:$phone'),
              ElevatedButton(
                onPressed: () async {
                  // Save the phone number
                  await AppCache.setPhone('137xxxxxxxx');
                  getPhone();
                },
                child: Text('save'),
              ),
              ElevatedButton(
                onPressed: () async {
                  // Clear the phone number
                  await AppCache.cleanPhone();
                  getPhone();
                },
                child: Text('clear'),),),),); }}Copy the code

• Attach the demo picture, click save, reopen the app, the phone number is still there, end. Thank you for watching, if there is a better way to achieve it, welcome to communicate with us