flutter-examples/firebase_google_authentication/lib/Screens/HomePage.dart

import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_google_authentication/Screens/InfoPage.dart';
import 'package:firebase_google_authentication/Screens/SignUpPage.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:google_fonts/google_fonts.dart';

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    final Size size = MediaQuery.of(context).size;
    return Scaffold(
      body: StreamBuilder(
          stream: FirebaseAuth.instance.authStateChanges(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return Center(
                child: CircularProgressIndicator(),
              );
            } else if (snapshot.hasError) {
              return Center(
                child: Text('An error Occured!!'),
              );
            } else if (snapshot.hasData) {
              return InfoPage();
            } else {
              return home(size, context);
            }
          }),
    );
  }

  Column home(Size size, BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text(
          'Welcome!',
          style: GoogleFonts.lora(
            fontSize: 36,
            fontWeight: FontWeight.w500,
          ),
        ),
        SizedBox(
          height: 30,
        ),
        SvgPicture.asset(
          'assets/login.svg',
          width: size.width * 0.8,
          height: size.height * 0.3,
        ),
        SizedBox(
          height: 60,
        ),
        Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            SizedBox(
              width: size.width * 0.8,
              child: ClipRRect(
                borderRadius: BorderRadius.circular(29),
                child: TextButton(
                  style: TextButton.styleFrom(
                      padding:
                          EdgeInsets.symmetric(vertical: 15, horizontal: 40),
                      backgroundColor: Color(0xFF6F35A5)),
                  onPressed: () {
                    Navigator.push(
                        context,
                        MaterialPageRoute(
                            builder: (context) => SignUpPage(true)));
                  },
                  child: Text(
                    'Login',
                    style: GoogleFonts.alice(
                        color: Colors.white,
                        fontWeight: FontWeight.bold,
                        fontSize: 20),
                  ),
                ),
              ),
            ),
          ],
        ),
        SizedBox(
          height: 15,
        ),
        SizedBox(
          width: size.width * 0.8,
          child: ClipRRect(
            borderRadius: BorderRadius.circular(29),
            child: TextButton(
              style: TextButton.styleFrom(
                  padding: EdgeInsets.symmetric(vertical: 15, horizontal: 40),
                  backgroundColor: Color(0xFFF1E6FF)),
              onPressed: () {
                Navigator.push(context,
                    MaterialPageRoute(builder: (context) => SignUpPage(false)));
              },
              child: Text(
                'SignUp',
                style: GoogleFonts.alice(
                    color: Colors.black,
                    fontWeight: FontWeight.bold,
                    fontSize: 20),
              ),
            ),
          ),
        ),
      ],
    );
  }
}