如何在React Native中的按下标签栏上添加事件

Question

我有一个React本机应用程序，其中我正在使用React Navigation V3。我想在按特定标签栏上创建一个事件。在我的家庭标签栏上，我有条形码扫描仪。当用户扫描时，该应用将带有条形码数据将数据设置为异步存储的其他选项卡。但是当我尝试再次扫描时，它会变为空白。

因此，我想创建一个事件，当用户转到Home Tab再次扫描时，我可以在其上清除异步存储。如何在家庭选项卡栏中添加该活动？

Answer 1

尝试以下代码，它将为您提供帮助，

import {NavigationEvents} from "react-navigation";

<NavigationEvents
      onWillFocus={payload => console.log('will focus',payload)}
      onDidFocus={payload => console.log('did focus',payload)}
      onWillBlur={payload => console.log('will blur',payload)}
      onDidBlur={payload => console.log('did blur',payload)}
    />

NavigationEvents组件您可以在要跟踪用户事件的页面渲染方法中添加，并像AsyncStorage一样处理和您想要的任何操作。

仅当您不需要全部时添加一个事件

有关更多详细信息，您可以在此处访问

谢谢

Answer 2

您可以侦听导航生命周期事件。

设置相当直接。这是如何在屏幕中设置它的示例。

import React, {Component} from 'react';
import { View, StyleSheet, Text } from 'react-native';
export default class Screen2 extends React.Component {
  // willFocus - the screen will focus
  // didFocus - the screen focused (if there was a transition, the transition completed)
  // willBlur - the screen will be unfocused
  // didBlur - the screen unfocused (if there was a transition, the transition completed)
  componentDidMount () {
    // add listener 
    this.willFocusSubscription = this.props.navigation.addListener('willFocus', this.willFocusAction);
    this.didFocusSubscription = this.props.navigation.addListener('didFocus', this.didFocusAction);
    this.willBlurSubscription = this.props.navigation.addListener('willBlur', this.willBlurAction);
    this.didBlurSubscription = this.props.navigation.addListener('didBlur', this.didBlurAction);
  }
  componentWillUmount () {
    // remove listener
    this.willFocusSubscription.remove()
    this.didFocusSubscription.remove();
    this.willBlurSubscription.remove();
    this.didBlurSubscription.remove();
  }
  willBlurAction = () => {
    console.log('willBlur Screen', new Date().getTime())
  }
  didBlurAction = () => {
    console.log('didBlur Screen', new Date().getTime());
  }
  didFocusAction = () => {
    console.log('didFocus Screen', new Date().getTime());
  }
  willFocusAction = () => {
    console.log('willFocus Screen', new Date().getTime());
  }

  render() {
    return (
      <View style={styles.container}>
      <Text>Screen</Text>
      </View>
    )
  }
}

您不需要添加所有听众，而只需添加所需的听众。您很可能需要从willFocus事件中的AsyncStorage中清除您的值。这样，它发生在屏幕焦点之前。