Flutter dynamic theming - Change theme at runtime using Provider

app.dart

import 'package:flutter/material.dart';

class AppProvider with ChangeNotifier {
  ThemeData _currentTheme;

  AppProvider() {
    _currentTheme = ThemeDat.light()
  }

  ThemeData get currentTheme => _currentTheme;

  set currentTheme(value) {
    _currentTheme = value;

    notifyListeners();
  }
}

home_screen.dart

import 'package:flutter/material.dart';

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: AppBar(
        title: Text('Example'),
      ),
      body: Container(
        padding: EdgeInsets.only(right: 15, left: 15),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FlatButton(
              child: Text('Dark'),
              onPressed: () {
                 appState.currentTheme = ThemeData.dark();
              },
            ),
          ],
        ),
      ),
    );
  }
}

main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:your_package/src/providers/app.dart';
import 'package:your_package/src/routes.dart';
import 'package:your_package/src/screens/home_screen.dart;

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(builder: (context) => AppProvider()),
      ],
      child: App(),
    );
  }
}
class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appState = Provider.of<AppProvider>(context);

    return MaterialApp(
      routes: routes,
      theme: appState.currentTheme,
      home: HomeScreen(),
    );
  }
}