App.js

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Image,
} from 'react-native';

import Login from './src/screens/Login';
import Secured from './src/screens/Secured';

export default class Main extends Component {
  state = {
    isLoggedIn: false
  }

  render() {

      if (this.state.isLoggedIn)
        return <Secured
        onLogoutPress={() => this.setState({isLoggedIn: false})}
        />;
      else
        return <Login
        onLoginPress={() => this.setState({isLoggedIn: true})}
        />;

  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#F5FCFF',
  },
});

AppRegistry.registerComponent('Main', () => Main);