reactjs - 使用 React Refs 触发命令式动画

Question

从文档中，有一个 Refs 用例:
Triggering imperative animations.
有人可以提供一个关于如何做到这一点的例子吗？在使用 Ref 将其滚动到 View 中后，我试图将用户的注意力吸引到 div 上，我认为这可能是一个理想的用例，也许吧？

Answer 1

见 Refs and the DOM , EventTarget.addEventListener() , 和 Element.getBoundingClientRect() 了解更多信息。

// Imperative Animation
class ImperativeAnimation extends React.Component {

  // State.
  state = {background: '#fff'}

  // Render.
  render = () => (
    <div ref={this.divRef} style={{height: '200vh', background: this.state.background}}>
      Scroll to turn background papayawhip.
    </div>
  )
  
  // Did Mount.
  componentDidMount() {
    window.addEventListener('scroll', this.onScroll)
  }
  
  // Div Ref.
  divRef = React.createRef()
  
  // On Scroll
  onScroll = event => {
    const div = this.divRef.current
    const {y} = div.getBoundingClientRect()
    if (y <= 0) this.setState({background: 'papayawhip'})
    else this.setState({background: '#fff'})
  }
  
}

// Mount.
ReactDOM.render(<ImperativeAnimation/>, document.querySelector('#root'))

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