小编Eit*_*itt的帖子

我在 react native app 的 componentDidMount 中添加了警报。警报显示然后用户第一次打开屏幕。当用户转到第二个屏幕，然后通过单击菜单再次返回到第一个屏幕时，未显示警报。请帮忙。

这是本机应用程序的反应。

import React, { Component } from 'react';

import { View, Image, TouchableOpacity, Alert } from 'react-native';

import {
  createDrawerNavigator,
  createStackNavigator,
  createAppContainer,
} from 'react-navigation';

import Screen1 from './pages/Screen1';
import Screen2 from './pages/Screen2';
import Screen3 from './pages/Screen3';

class NavigationDrawerStructure extends Component {

  toggleDrawer = () => {
    //Props to open/close the drawer
    this.props.navigationProps.toggleDrawer();
  };
  render() {
      Alert.alert("hello");
    return (
      <View style={{ flexDirection: 'row' }}>
        <TouchableOpacity onPress={this.toggleDrawer.bind(this)}>
          {/*Donute Button Image */}
          <Image
            source={require('./image/drawer.png')}
            style={{ …