manual-auth-check.tsx

export const App = () => {
  const [authState, setAuthState] = React.useState<AuthState>();
  const [user, setUser] = React.useState<object | undefined>();

  useEffect(() => {
    return onAuthUIStateChange((nextAuthState, authData) => {
      setAuthState(nextAuthState);
      setUser(authData);
    });
  }, []);

  return authState === AuthState.SignedIn && user ? (
    <BrowserRouter>
      <Switch>
        <Route path="/" component={Dashboard} />
      </Switch>
    </BrowserRouter>
  ) : (
    <AmplifyAuthenticator>
      <AmplifySignUp
        headerText="Sign Up"
        slot="sign-up"
        formFields={signUpFields}
      ></AmplifySignUp>
      <AmplifySignIn
        headerText="Log in to Dashboard"
        slot="sign-in"
        formFields={signInFields}
      ></AmplifySignIn>
    </AmplifyAuthenticator>
  );
};