App.js

// In App.js in a new project

import * as React from 'react';
//import { View, Text } from 'react-native';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';

import OnboardingScreen from './screens/OnboardingScreen';
import LoginScreen from './screens/LoginScreen';
import { useEffect } from 'react';
import AsyncStorage from '@react-native-community/async-storage';


const AppStack = createStackNavigator();

const  App=()=> {
  const [isFirstLaunch,setIsFirstLaunch]=React.useState(null);

  useEffect(()=>{
    AsyncStorage.getItem('alreadyLaunched').then(value=>{
      if(value === null){
       AsyncStorage.setItem('alreadyLaunched','true');
       setIsFirstLaunch(true);
      } else{
       setIsFirstLaunch(false);
      }
    })

  },[]);

  if(isFirstLaunch===null){
    return null;
  } else if(isFirstLaunch===true){
    return(
      <NavigationContainer>
      <AppStack.Navigator
       headerMode='none'
      >
        <AppStack.Screen name="Onboarding" component={OnboardingScreen} />
        <AppStack.Screen name="Login" component={LoginScreen}/>
      </AppStack.Navigator>
    </NavigationContainer>

    );
  }
  else{
   return <LoginScreen/>;
  }

  // return (
  //   <NavigationContainer>
  //     <AppStack.Navigator
  //      headerMode='none'
  //     >
  //       <AppStack.Screen name="Onboarding" component={OnboardingScreen} />
  //       <AppStack.Screen name="Login" component={LoginScreen}/>
  //     </AppStack.Navigator>
  //   </NavigationContainer>
  // );
}

export default App;