警报提示功能不起作用反应原生 [英] Alert prompt to function not working in react native

问题描述

我的页面上有一个按钮，提示提醒。如果该用户选择是，那么我想要运行 exit（）函数。但是，它现在编码的方式，由于某种原因没有任何反应。

I have a button on my page that prompts an alert. If that user selects Yes, I then want the exit() function to run. However, the way it is coded now, for some reason nothing happens.

有谁知道我做错了什么？

Does anyone know what I am doing wrong?

import React, { Component } from 'react';
import { ActivityIndicator, AsyncStorage, Button, StatusBar, Text, StyleSheet, View, TextInput, Alert } from 'react-native';

type Props = {};
export default class IDScreen extends Component<Props> {

  static navigationOptions = {
    title: 'Identification',
  };

  exit = async () => {
    alert("I should see this but I don't");
    await AsyncStorage.clear();
    this.props.navigation.navigate('Login');
  }

  promptExit() {
    Alert.alert("Are you sure?", "You can't be serious.", [
      {text: 'Yes, Sign out', onPress: async () => this.exit },
      {text: 'Cancel', onPress: () => console.log('Cancel Pressed'), style: 'cancel'},
    ],
    { cancelable: true });
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.footerText} onPress={this.promptExit}>Sign Out</Text>
      </View>

    );
  }

}

推荐答案

您需要将 promptExit（）修改为箭头函数 promptExit =（）=> 。

You need to modify promptExit() to an arrow function promptExit = () =>.

使用箭头函数，不要在其体内重新定义此 的值，它只是意味着函数体内的与它之外的相同。

因为函数被调用而没有引用特定的对象，如 yourObj.yourMethod（），因此您需要在类中 bind 它构造函数/渲染或使用箭头函数。

Since the function is called without its reference to a particular object, like yourObj.yourMethod(), therefore you either need to bind it in the class constructor / render or use arrow function.

没有它，它会丢失它的上下文并始终是 undefined 或全局对象。

Without it , it would lose it's context and will always be undefined or a global object.

同样，你也可以阅读

何时不使用箭头功能

这篇关于警报提示功能不起作用反应原生的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！