prefnotifiers 1.0.8+1

Represents shared preferences as ValueNotifier objects. Reads and writes occur asynchronously in background.

example/lib/example.dart

import 'package:flutter/material.dart';
import 'package:prefnotifiers/prefnotifiers.dart';

void main() => runApp(new MyApp());

// this int value will be stored permanently in shared preferences
final pushesCountPref = PrefNotifier<int>('ButtonPushesCount');

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

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
          Text('You have pushed the button this many times:'),

          // SHOWING THE VALUE
          // the following widget will be automatically rebuilt when
          // PrefNotifier finishes loading and/or when its value changes
          ValueListenableBuilder(
              valueListenable: pushesCountPref,
              builder: (context, value, child) =>
                  Text(pushesCountPref.value.toString())),

          // CHANGING THE VALUE
          MaterialButton(
              child: Text("Increment and save"),
              color: Colors.amberAccent,
              onPressed: () async {
                // make sure the value is already loaded
                await pushesCountPref.initialized;

                // update the value
                pushesCountPref.value = (pushesCountPref.value ?? 0) + 1;

                // ok, the value is already increased (widgets will see
                // it on the next frame). Asynchronous writing of it in
                // the SharedPreferences has also begun.
                //
                // By the way, awaiting for pushesCountPref.initialized
                // was optional. PrefNotifier didn't need it.
                //
                // But our program could calculate the wrong new value,
                // taking null for 0, when it just meant "not loaded yet".
              })
        ])));
  }
}