Local storage

If you don’t need to store a lot of data and it doesn’t require structure, you can use shared_preferences which allows you to read and write persistent key-value pairs of primitive data types: booleans, floats, ints, longs, and strings.

How do I store persistent key-value pairs that are global to the app?

In React Native, you use the setItem and getItem functions of the AsyncStorage component to store and retrieve data that is persistent and global to the app.

// React Native
await AsyncStorage.setItem( 'counterkey', json.stringify(++this.state.counter));
AsyncStorage.getItem('counterkey').then(value => {
  if (value != null) {
    this.setState({ counter: value });
  }
});

In Flutter, use the shared_preferences plugin to store and retrieve key-value data that is persistent and global to the app. The shared_preferences plugin wraps NSUserDefaults on iOS and SharedPreferences on Android, providing a persistent store for simple data. To use the plugin, add shared_preferences as a dependency in the pubspec.yaml file then import the package in your Dart file.

dependencies:
  flutter:
    sdk: flutter
  shared_preferences: ^0.4.3

// Dart
import 'package:shared_preferences/shared_preferences.dart';

To implement persistent data, use the setter methods provided by the SharedPreferences class. Setter methods are available for various primitive types, such as setInt, setBool, and setString. To read data, use the appropriate getter method provided by the SharedPreferences class. For each setter there is a corresponding getter method, for example, getInt, getBool, and getString.

SharedPreferences prefs = await SharedPreferences.getInstance();
_counter = prefs.getInt('counter');
prefs.setInt('counter', ++_counter);
setState(() {
  _counter = _counter;
});