mobile_nebula/lib/main.dart

import 'package:flutter/cupertino.dart' show CupertinoThemeData, DefaultCupertinoLocalizations;
import 'package:flutter/material.dart'
    show BottomSheetThemeData, Colors, DefaultMaterialLocalizations, Theme, ThemeData, ThemeMode;
import 'package:flutter/scheduler.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_platform_widgets/flutter_platform_widgets.dart';
import 'package:mobile_nebula/screens/MainScreen.dart';
import 'package:mobile_nebula/services/settings.dart';

//TODO: EventChannel might be better than the streamcontroller we are using now

void main() => runApp(Main());

class Main extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) => App();
}

class App extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<App> {
  final settings = Settings();
  Brightness brightness = SchedulerBinding.instance.window.platformBrightness;

  @override
  void initState() {
    //TODO: wait until settings is ready?
    settings.onChange().listen((_) {
      setState(() {
        if (!settings.useSystemColors) {
          brightness = settings.darkMode ? Brightness.dark : Brightness.light;
        }
      });
    });

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    final ThemeData lightTheme = ThemeData(
      brightness: Brightness.light,
      primarySwatch: Colors.blueGrey,
      primaryColor: Colors.blueGrey[900],
      primaryColorBrightness: Brightness.dark,
      accentColor: Colors.cyan[600],
      accentColorBrightness: Brightness.dark,
      fontFamily: 'PublicSans',
      //scaffoldBackgroundColor: Colors.grey[100],
      scaffoldBackgroundColor: Colors.white,
      bottomSheetTheme: BottomSheetThemeData(
        backgroundColor: Colors.blueGrey[50],
      ),
    );

    final ThemeData darkTheme = ThemeData(
      brightness: Brightness.dark,
      primarySwatch: Colors.grey,
      primaryColor: Colors.grey[900],
      primaryColorBrightness: Brightness.dark,
      accentColor: Colors.cyan[600],
      accentColorBrightness: Brightness.dark,
      fontFamily: 'PublicSans',
      scaffoldBackgroundColor: Colors.grey[800],
      bottomSheetTheme: BottomSheetThemeData(
        backgroundColor: Colors.grey[850],
      ),
    );

    // This theme is required since icons light/dark mode will look for it
    return Theme(
      data: brightness == Brightness.light ? lightTheme : darkTheme,
      child: PlatformProvider(
        //initialPlatform: initialPlatform,
        builder: (context) => PlatformApp(
          localizationsDelegates: <LocalizationsDelegate<dynamic>>[
            DefaultMaterialLocalizations.delegate,
            DefaultWidgetsLocalizations.delegate,
            DefaultCupertinoLocalizations.delegate,
          ],
          title: 'Nebula',
          android: (_) {
            return new MaterialAppData(
              themeMode: brightness == Brightness.light ? ThemeMode.light : ThemeMode.dark,
            );
          },
          ios: (_) => CupertinoAppData(
            theme: CupertinoThemeData(brightness: brightness),
          ),
          home: MainScreen(),
        ),
      ),
    );
  }
}