App.js

import 'react-native-gesture-handler'
import { NavigationContainer, useNavigation } from '@react-navigation/native';
import React, { useEffect, useState, createContext } from 'react'
import { StyleSheet } from 'react-native'
import { createNativeStackNavigator } from '@react-navigation/native-stack';

import { auth } from './firebase'

import NavigationHome from './screens/NavigationHome';
import NavigationLogin from './screens/NavigationLogin';

import AsyncStorage from '@react-native-async-storage/async-storage';

Stack = createNativeStackNavigator()


function App() {

  const [userFullName, setUserFullName] = useState('')


  const storeStringData = async (key, value) => {
    try {
      await AsyncStorage.setItem(key, value)
      console.log(`Successfully stored ${key} : ${value}`)
    } catch (e) {
      console.log("Stored UID Successfully")
      // saving error
    }
  }


  console.log(auth)
  const [initializing, setInitializing] = useState(true);
  const [user, setUser] = useState();

  // Handle user state changes
  function onAuthStateChanged(user) {
    setUser(user);
    if (user){
      storeStringData("userID", user.uid)
      console.log(user)
      storeStringData("userFullName", user.displayName)
    }
    else storeStringData("userID", null)
    if (initializing) setInitializing(false);
  }

  useEffect(() => {
    const subscriber = auth.onAuthStateChanged(onAuthStateChanged);
    return subscriber; // unsubscribe on unmount
  }, []);

  if (!user) {
    return (
      <NavigationContainer>
        <Stack.Navigator>
          <Stack.Screen options={{ headerShown: false }} name="LoginScreenStack" component={NavigationLogin} />
        </Stack.Navigator>
      </NavigationContainer>
    )
  }
  return (
    <NavigationContainer>
      <Stack.Navigator>
        <Stack.Screen options={{ headerShown: false }} name="HomeScreenStack" component={NavigationHome} />
      </Stack.Navigator>
    </NavigationContainer>
  )
}

export default App

const styles = StyleSheet.create({})