问成功登录后，应用程序栏中的back按钮(我没有使用导航)

EN

class Page5 extends StatefulWidget {
  const Page5({Key? key}) : super(key: key);

  @override
  State<Page5> createState() => _Page5State();
}

class _Page5State extends State<Page5> {
  final providerConfigs = [EmailProviderConfiguration()];

  @override
  Widget build(BuildContext context) {
    return
      FirebaseAuth.instance.currentUser == null
        ? Page5_null()
        : Page5_on();
}
}

class Authentication extends StatelessWidget {
  const Authentication({Key? key}) : super(key: key);


  @override
  Widget build(BuildContext context) {
    return StreamBuilder(
      stream: FirebaseAuth.instance.authStateChanges(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) { 
          return SignInScreen(
            providerConfigs: [EmailProviderConfiguration()],);
        }
        return  HomePage();
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  var _index = 0;
  final _pages = [
    Ppage1(),
    const Page2(),
    const Page3(),
    const Page4(),
    const Page5(),
  ]; ...