引用错误： 找不到变量

Question

所以我是 React Native 的新手，但每次我从 Facebook React Native 文档中放置一个新的组件(如按钮或图像(时，我都会在模拟器上收到"参考错误：找不到变量"错误？老实说，当我添加除文本以外的任何其他代码时，就会发生这种情况。我没有错误地链接某些东西吗？任何事情都会有所帮助。

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */
import React, { Component } from 'react';
import {
  Platform,
  StyleSheet,
  Text,
  View
} from 'react-native';
const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,n' +
    'Cmd+D or shake for dev menu',
  android: 'Double tap R on your keyboard to reload,n' +
    'Shake or press menu button for dev menu',
});
export default class App extends Component<{}> {
  render() {
    return (
        <View style={styles.container}>
        
        <Text style={styles.welcome}>
          This is a new App!
        </Text>
        <Text style={styles.instructions}>
          To get started, edit App.js
        </Text>
        <Text style={styles.instructions}>
          {instructions}
        </Text>
        <Button
  onPress={onPressLearnMore}
  title="Learn More"
  color="#841584"
  accessibilityLabel="Learn more about this purple button"
/>
        <Text style={{color: 'blue'}}>Hello</Text>
      </View>
        
    );
  }
}
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: 'white',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});

**错误这是错误

Answer 1

尝试将Button添加到导入中，如下所示：

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