30秒学会 React 片段 – React useRequestAnimationFrame hook

Runs an animating function, calling it before every repaint.

• Use the useRef() hook to create two variables. requestRef will hold the last request id and previousTimeRef will hold the last timestamp.
• Define a function, animate, which handles updating these variables, runs the callback and calls Window.requestAnimationFrame() perpetually.
• Use the useEffect() hook with an empty array to initialize the value of requestRef using Window.requestAnimationFrame(). Use the returned value and Window.cancelAnimationFrame() to clean up when the component unmounts.

代码实现

const useRequestAnimationFrame = callback => {
  const requestRef = React.useRef();
  const previousTimeRef = React.useRef();

  const animate = time => {
    if (previousTimeRef.current) callback(time - previousTimeRef.current);
    previousTimeRef.current = time;
    requestRef.current = requestAnimationFrame(animate);
  };

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

使用样例

const Counter = () => {
  const [count, setCount] = React.useState(0);

  useRequestAnimationFrame(deltaTime => {
    setCount(prevCount => (prevCount + deltaTime * 0.01) % 100);
  });

  return <p>{Math.round(count)}</p>;
};

ReactDOM.createRoot(document.getElementById('root')).render(
  <Counter />
);

翻译自：https://www.30secondsofcode.org/react/s/use-request-animation-frame