React 16.8 方法是通过改变父组件传给子组件的值会使子组件重新render触发子组件的useEffect事件

父组件

import React, { useState } from 'react'
import Child from './index.js'
 
function Father () {
    const [toChildNum, setToChildNum] = useState(0)
 
    return (
        <div>
            <button
                onPress={() => {
                    setToChildNum(toChildNum + 1)
                }}
            >
                点击调用子组件方法
            </button>
            <Child num={toChildNum} />
        </div>
    )
}
 
export default Father;

子组件

import React, { useEffect } from 'react'
 
function Child ({ num }) {
 
    useEffect(() => {
        alert('我被调用了')
    }, [num])
 
    return  (
        <div>子组件</div>
    )
}