import 'package:flutter/material.dart';

class SignInScreen extends StatefulWidget {
  @override
  _SignInScreenState createState() => _SignInScreenState();
}

class _SignInScreenState extends State<SignInScreen> {

  PageStatus pageStatus = PageStatus.signingIn;

  @override
  Widget build(BuildContext context) {
    return pageStatus == PageStatus.signingIn ? SignInPage(this.updateStatus) : CreateNewPage(this.updateStatus);
  }

  void updateStatus(PageStatus newStatus) {
    setState(() {
      pageStatus = newStatus;
    });
  }
}




enum PageStatus {
  signingIn,
  creatingNew
}


class SignInPage extends StatelessWidget {
  SignInPage(this.updatePageStatus);

  final Function updatePageStatus;

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

class CreateNewPage extends StatelessWidget {
  CreateNewPage(this.updatePageStatus);

  final Function updatePageStatus;

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}