参考错误:找不到变量 [英] ReferenceError: Can't Find Variable

问题描述

所以我是 React Native 的新手，但是每次我从 Facebook 的 React Native Doc's 放置一个新组件(如按钮或图像)时，我都会在模拟器上收到ReferenceError:Can't Find Variable"错误?老实说，当我添加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.

So i'm new to React Native but every time i put a new Component like a Button or an Image from Facebooks React Native Doc's i keep getting a "ReferenceError : Can't Find Variable" error on the simulator? This honestly happens when i add any other piece of code other than Text. Am i not linking something incorrectly? Anything would help.

/**
 * 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

推荐答案

尝试将 Button 添加到导入中，如下所示:

Try adding Button to the import like so:

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

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