Starts in portrait mode by default

[dpadhiyar]

 @override
  void initState() {
    WidgetsBinding.instance.addObserver(this);
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((Duration duration) async {
      await SystemChrome.setPreferredOrientations(
          <DeviceOrientation>[DeviceOrientation.portraitUp]);
      SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.light
          .copyWith(statusBarColor: Colors.transparent));
    });
  }

How to set landscape mode by default?