Storing a username on sign up only displays after page refresh (Firebase)

Question

I'm new to React and Firebase, and I've been trying to solve this small User Sign-Up problem all day . Hopefully someone can help me out, I'd be so grateful

I am making a twitter-like blog site with react and Firebase, and am currently using Firebase's auth.createUserWithEmailAndPassword() method to register a new user, with a username. This is how I'm doing it:

  import { auth } from '../firebase';

  const onSubmit = async (data) => {
    auth
      .createUserWithEmailAndPassword(data.email, data.password)
      .then((result) => {
        result.user.updateProfile({
          displayName: data.username,
        });
        setUserError(!userError);
        window.localStorage.setItem('emailForSignIn', data.email);
        setRedirect(true);
      })
      .catch((error) => {
        setUserError(!userError);
        setAlertMsg(error.message);
      });
  };

After the user submits the form, they are redirected to the main page, which I then set the page to their current username. I'm setting the username by setting a state for it, and then passing it as a prop to all my pages.

const Main = ({SignOut}) => {
  const [userName, setUserName] = useState('')


  useEffect(() => {
    const getUserName = () => {
      auth.onAuthStateChanged((user) => {
        setUserName(user.displayName)
        console.log('Current userName is: ', user.displayName);
      });
    }
    getUserName() 
  }, [])
  
    return (
    <Router>
      <Switch>
          <Route exact path="/">
            <Navbar userName={userName} SignOut={SignOut} />
            <Tweets userName={userName} />
          </Route>
          <Route path="/profile">
            <Navbar userName={userName} SignOut={SignOut} />
            <Profile setUserName={setUserName} userName={userName} />
          </Route>
        </Switch>
    </Router>
  )
}

Almost everything works perfectly, however their username only shows up if they log out and log back in. Any help would be awesome!

EDIT

Here is my App Component. I moved the useEffect event here, however, I am still experiencing the same thing.

 function App() { const [user] = useAuthState(auth); const [userName, setUserName] = useState(''); useEffect(() => { const getUserName = () => { auth.onAuthStateChanged((user) => { setUserName(user.displayName); console.log('Current userName is: ', user.displayName); }); }; getUserName(); }, []); return ( <> {user? ( <Main userName={userName} setUserName={setUserName} SignOut={SignOut} /> ): ( <Register /> )} </> ); }

Answer 1

This was a super noob bug that I was experiencing, but instead of using useEffect to set the username, I just passed my setUserName state to my sign up component, and did away with useEffect entirely. This fixed everything.

 const onSubmit = async (data) => { auth.createUserWithEmailAndPassword(data.email, data.password).then((result) => { result.user.updateProfile({ displayName: data.username, }); // This is the state i was missing. setUserName(data.username); setUserError(;userError). window.localStorage,setItem('emailForSignIn'. data;email); setRedirect(true); })