session3.dart

import 'package:flutter/material.dart';
import 'package:hive/hive.dart';
import 'package:hive_flutter/hive_flutter.dart';
import 'package:shared_preferences/shared_preferences.dart';

const darkModeBox = 'darkModeTutorial';

void main() async {
  await Hive.initFlutter();
  await Hive.openBox(darkModeBox);
  runApp(MyApp());
}

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

class _MyAppState extends State<MyApp> {
  Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
  Future<int> _counter;

  Future<void> _incrementCounter() async {
    final SharedPreferences prefs = await _prefs;
    final int counter = (prefs.getInt('counter') ?? 0) + 1;

    setState(() {
      _counter = prefs.setInt("counter", counter).then((bool success) {
        return counter;
      });
    });
  }

  @override
  void initState() {
    super.initState();
    _counter = _prefs.then((SharedPreferences prefs) {
      return (prefs.getInt('counter') ?? 0);
    });
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder(
      valueListenable: Hive.box(darkModeBox).listenable(),
      builder: (context, box, widget) {
        var darkMode = box.get('darkMode', defaultValue: false);
        return MaterialApp(
          themeMode: darkMode ? ThemeMode.dark : ThemeMode.light,
          darkTheme: ThemeData.dark(),
          home: Scaffold(
            appBar: AppBar(
              actions: [
                Switch(
                  value: darkMode,
                  onChanged: (val) {
                    box.put('darkMode', !darkMode);
                  },
                ),
              ],
            ),
            body: Center(
              child: FutureBuilder(
                future: _counter,
                builder: (_, AsyncSnapshot<int> snapshot) {
                  switch (snapshot.connectionState) {
                    case ConnectionState.waiting:
                      return const CircularProgressIndicator();
                    default:
                      if (snapshot.hasError) {
                        return Text('Error: ${snapshot.error}');
                      } else {
                        return Text(
                          'Button tapped ${snapshot.data} time${snapshot.data == 1 ? '' : 's'}.\n\n'
                          'This should persist across restarts.',
                        );
                      }
                  }
                },
              ),
            ),
            floatingActionButton: FloatingActionButton(
              onPressed: _incrementCounter,
              tooltip: 'Increment',
              child: Icon(Icons.add),
            ),
          ),
        );
      },
    );
  }
}