javascript - React useEffect 中的间隔 - 将其存储在 useRef Hook 中以保留值超时警告
问题描述
所以我有这个方法:
useEffect(() => {
//.. other logic here
// Firefox doesn't support looping video, so we emulate it this way
video.addEventListener(
"ended",
function() {
video.play();
},
false
);
}, [videoWidth, videoHeight]);
现在它抛出一个错误,它说:
Assignments to the 'interval' variable from inside React Hook useEffect will be lost after each render. To preserve the value over time, store it in a useRef Hook and keep the mutable value in the '.current' property. Otherwise, you can move this variable directly inside useEffect.
我很困惑这是什么意思?特别是这部分:To preserve the value over time, store it in a useRef Hook and keep the mutable value in the '.current' property
。
解决方案
错误将您指向正确的方向。使用useRef
挂钩来引用视频元素。由于该handleVideo
函数使 useEffect Hook 的依赖关系在每次渲染时都会发生变化,我们将handleVideo
定义包装到它自己的useCallback()
Hook 中。
import React, { useEffect, useRef, useCallback } from "react";
function Video() {
const videoRef = useRef(null);
const handleVideo = useCallback(() => {
videoRef.current.play()
}, [])
useEffect(() => {
const video = videoRef.current
video.addEventListener('ended', handleVideo)
return () => {
video.removeEventListener('ended', handleVideo)
}
}, [handleVideo])
return <video width="400" controls ref={videoRef} src="https://www.w3schools.com/html/mov_bbb.mp4" />
}