Question

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]);

现在它在显示以下内容的地方抛出错误：

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.

我对这是什么意思感到困惑？尤其是这部分：To preserve the value over time, store it in a useRef Hook and keep the mutable value in the '.current' property。

Answer 1

错误将您指向正确的方向。使用useRef钩子引用视频元素。由于handleVideo函数在每个渲染器上都改变了useEffect Hook的依赖关系，因此我们将handleVideo定义包装到了自己的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" />
}

Answer 2

尝试这种方式会起作用

const video = useRef(null);
const videoPlay = () => { //just hate stateFull Function
        video.current.play();
      }
useEffect(() => {
    //.. other logic here

    // Firefox doesn't support looping video, so we emulate it this way
    video.addEventListener(
      "ended",
      videoPlay,
      false
    );
    return video.removeEventListener("ended", videoPlay, true)
  }, [videoWidth, videoHeight, video]);

   <video ref={video}>
      <source src={src} type="video/mp4" />
   </video>

如果将代码放入jsfiddle或类似的地方，我们可以为您提供更多帮助

React useEffect内部的时间间隔-将其存储在useRef Hook中以保留值超时警告

2 个答案: