useEffect 没有更新依赖值

Question

我有一个要动态编辑某些样式的组件。 当我进入组件时，我希望它顺利增长，而当我离开时，我希望它顺利缩短。

这是我的代码：

  const easing = 0.1;
  const outScale = 0.6;
  const inScale = 1;
  let targetScale = outScale;
  let elementScale = targetScale;
  let innerScale = 1 / elementScale;

  const [parentTransformStyle, setParentTransformStyle] = useState(
    `scale(${elementScale})`
  );
  const [innerTransformStyle, setInnerTransformStyle] = useState(
    `scale(${innerScale})`
  );
  const requestRef = useRef();

  const onPointOverEvent = () => {
    targetScale = inScale;
    console.log("over", inScale, targetScale);
  };

  const onPointerOutEvent = () => {
    targetScale = outScale;
    console.log("out", outScale, targetScale);
  };

  const animate = () => {
    console.log("animate", targetScale);

    elementScale += (targetScale - elementScale) * easing;
    innerScale = 1 / elementScale;

    setParentTransformStyle(`scale(${elementScale})`);
    setInnerTransformStyle(`scale(${innerScale})`);

    requestAnimationFrame(animate);
  };

  useEffect(() => {
    requestRef.current = requestAnimationFrame(animate);
    return () => cancelAnimationFrame(requestRef.current);
  }, []);

变量targetScale应该在鼠标悬停在元素中和鼠标离开元素时更新。

如果我在事件侦听器中打印值，则该值是正确的。 但是在animate函数内部，它具有初始值。 有人可以指出我缺少的东西吗？

Answer 1

有什么理由不能使用 CSS 转换而不是自己制作动画？

例子：

 function MyComponent() { const [innerTransformStyle, setInnerTransformStyle] = React.useState( `scale(${0.6})` ); const onPointOverEvent = () => { setInnerTransformStyle(`scale(${1})`); }; const onPointerOutEvent = () => { setInnerTransformStyle(`scale(${0.6})`); }; return ( <div className="parent"> <div className="element" style={{transform: innerTransformStyle}} onPointerOut={onPointerOutEvent} onPointerOver={onPointOverEvent}></div> </div> ); } ReactDOM.render(<MyComponent/>, document.getElementById("app"));

 .parent { width: 100px; height: 100px; background-color: #f00; } .element { width: 100px; height: 100px; background-color: #0f0; transition: transform 1s; }

 <script src="https://unpkg.com/react@16/umd/react.development.js" crossorigin></script> <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js" crossorigin></script> <div id="app"></div>