How to solve "Can't find variable: App" in React Native?

Question

I am new to React Native and I don't understand how to solve this problem. I already installed react-native-gesture-handler . I am getting this error in the command:

Accessing view manager configs directly off UIManager via UIManager['getConstants'] is no longer supported. Use UIManager.getViewManagerConfig('getConstants') instead.

This is a part of the code:

import { createAppContainer, DrawerNavigator } from 'react-navigation';
import { createStackNavigator } from 'react-navigation-stack';
import Home from "./src/screens/Home.js";
import first from "./src/screens/first.js";
import React from 'react';

class App extends React.Component{
  render(){
    return(
      <RootStack/>
    )
  }
}

const RootStack = createStackNavigator ({

  Home:{screen:Home,
    navigationOptions: {
      header: null
     }},
  first:{screen:first,
    navigationOptions: {
      header: null
     }}

});

//const App = createAppContainer(RootStack);
export default App;

Answer 1

I think this way is better:

const AppNavigator = createSwitchNavigator({
  Auth: {
    screen: Auth
  },
  Root: {
    screen: BottomTabNavigator
  }
})

const AppContainer = createAppContainer(AppNavigator)

const App = () => {
  return (
    <AppContainer />
  )
}

export default App

OR

if it didn't work then you better check your index.js file whether you imported App Component (Root component) correctly or not?