Async app init

main.dart

// ...
  
class _RootState extends State<RootWidget> {
  TenderApiProvider tenderApi = TenderApiProvider();
  AppState state = AppState();

  Future init() async {
    return Future.wait(<Future>[
      tenderApi.init(), // fetch and store token
      Future.delayed(const Duration(milliseconds: 2000)) // Let user see the splash for couple of seconds
    ]);
  }

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(builder: (_) => tenderApi),
        ChangeNotifierProvider(builder: (_) => state),
      ],
      child: MaterialApp(title: "My App"), 
      routes: <String, WidgetBuilder>{
        '/': _buildLoading
      },
      ),
    );
  }

  Widget _buildLoading(BuildContext context) {
    return FutureBuilder(
      future: init(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        if (snapshot.hasData) {
          // All good, show user actual home screen
          return HomeScreen();
        } else if (snapshot.hasError) {
          // Application probably won't run as expected
          // as init has failed.
          return ErrorScreen();
        }

        return LoadingScreen();
      },
    );
  }
}