问如何解决固定冲突:文本字符串必须在React Native中的<Text>组件中呈现？

EN

import React, { Component } from "react";
import {
    View,
    StyleSheet,
    Button
} from "react-native";

class WelcomeScreen extends Component {

    static navigationOptions = {
        header: 'none'
    }

    render() {
        return (
            <View style={styles.container}>
                <Button title="Log in" onPress={() => this.props.navigation.navigate('LoginScreen')}/>
                <Button title="Sign Up" onPress={() => this.props.navigation.navigate('SignUpScreen')}/>
            </View>
        )
    }
}
export default WelcomeScreen;

const styles = StyleSheet.create({
    container: {
        flex: 1,
        alignItems: 'center',
        justifyContent: 'center'
    }
});

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

import { StackNavigator } from 'react-navigation'
import WelcomeScreen from './screens/WelcomeScreen'
export default class App extends React.Component {
  render() {
    return (
      <AppStackNavigator/>
    );
  }
}

const AppStackNavigator = new StackNavigator({
  WelcomeScreen: { screen: WelcomeScreen }
})


const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});