App.js

import * as React from 'react';
import { Root } from "native-base";
import { AppLoading } from 'expo';
import * as Font from 'expo-font';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { Ionicons } from '@expo/vector-icons';
import Home from './Home';
import Summary from './Summary';
import Review from './Review';
//import styles from './styles';

export default class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      isReady: false,
    };
  }

  async componentDidMount() {
    await Font.loadAsync({
      Roboto: require('native-base/Fonts/Roboto.ttf'),
      Roboto_medium: require('native-base/Fonts/Roboto_medium.ttf'),
      ...Ionicons.font,
    });
    this.setState({ isReady: true });
  }

  render() {
    const Stack = createStackNavigator();

    if (!this.state.isReady) {
      return <AppLoading />;
    }

    return (
      <Root>
        <NavigationContainer>
          <Stack.Navigator screenOptions={{ headerShown: false }}>
            <Stack.Screen name="Home" component={Home} />
            <Stack.Screen name="Summary" component={Summary} />
            <Stack.Screen name="Review" component={Review} />
          </Stack.Navigator>
        </NavigationContainer>
      </Root>
    );
  }
}