如何在反应原生 Es6 上检测 OnResume 和 onPause答案

【问题标题】：How to detect OnResume and onPause on react native Es6如何在反应原生 Es6 上检测 OnResume 和 onPause
【发布时间】：2018-10-05 19:35:52
【问题描述】：

如何检测从后台到前台 es6 的任何方法？

这在 React-native 中可行吗？是否有任何类或工具可以帮助这种类型的方法？

【问题讨论】：

标签： android react-native-android onresume onpause

【解决方案1】：

试试这个，它对我有用

import React, {Component} from 'react'
import {AppState, Text} from 'react-native'

class AppStateExample extends Component {

  state = {
    appState: AppState.currentState
  }

  componentDidMount() {
    AppState.addEventListener('change', this._handleAppStateChange);
  }

  componentWillUnmount() {
    AppState.removeEventListener('change', this._handleAppStateChange);
  }

  _handleAppStateChange = (nextAppState) => {
    if (this.state.appState.match(/inactive|background/) && nextAppState === 'active') {
      console.log('App has come to the foreground!')
    }
    this.setState({appState: nextAppState});
  }

  render() {
    return (
      <Text>Current state is: {this.state.appState}</Text>
    );
  }

}

【讨论】：

组件状态呢？就像如果我们加载一个场景并在它上面加载另一个场景！是否有任何触发方法，如 onPause OnResume 特定于组件而不是特定于 App？

【解决方案2】：

作为对现有答案的更新，removeEventListener(type, handler) 已成为 deprecated（自 2021 年 9 月起）：

对返回的事件订阅使用 remove() 方法 addEventListener()

使用类组件

import React, {Component} from 'react'
import {AppState, Text} from 'react-native'

class AppStateExample extends Component {

  state = {
    appState: AppState.currentState
  }

  eventListenerSubscription = null;

  componentDidMount() {
    this.eventListenerSubscription = AppState.addEventListener('change', this._handleAppStateChange);
  }

  componentWillUnmount() {
    this.eventListenerSubscription.remove();
  }

  _handleAppStateChange = (nextAppState) => {
    if (this.state.appState.match(/inactive|background/) && nextAppState === 'active') {
      console.log('App has come to the foreground!')
    }
    this.setState({appState: nextAppState});
  }

  render() {
    return (
      <Text>Current state is: {this.state.appState}</Text>
    );
  }
}

使用钩子

import React, { useState, useEffect } from 'react';
import { AppState, Text } from 'react-native';

function AppStateExample() {
  const [appState, setAppState] = useState(AppState.currentState);
  var eventListenerSubscription;

  const _handleAppStateChange = nextAppState => {
    if (appState.match(/inactive|background/) && nextAppState === 'active') {
      console.log('App has come to the foreground!');
    }
    setAppState(nextAppState);
  };

  useEffect(() => {
    //on mount
    eventListenerSubscription = AppState.addEventListener('change', _handleAppStateChange);
    return () => {
      // on unmount
      eventListenerSubscription.remove();
    };
  }, []);

  return <Text>Current state is: {appState}</Text>;
}
export default AppStateExample;

【讨论】：