获取React中div的offsetTop位置

Z时代
2024-01-10
分类：问答

我正在尝试在React中实现一个List视图。我想要实现的是存储列表标头信息并注册组件并注册滚动事件。每次用户滚动窗口时，我都想取出存储的div并重新计算offsetTop数据。

现在的问题是，我发现控制台仅打印出初始值（该值是固定的，并且从未更改），offsetTop数据onscroll功能从未更改。

有人建议如何offsetTop从_instances对象获取最新信息吗？

import React, { Component } from 'react';
import ListHeader from './lib/ListHeader';
import ListItems from './lib/ListItems';
const styles = {
  'height': '400px',
  'overflowY': 'auto',
  'outline': '1px dashed red',
  'width': '40%'
};
class HeaderPosInfo {
  constructor(headerObj, originalPosition, originalHeight) {
    this.headerObj = headerObj;
    this.originalPosition = originalPosition;
    this.originalHeight = originalHeight; 
  }
}
export default class ReactListView extends Component {
  static defaultProps = {
    events: ['scroll', 'mousewheel', 'DOMMouseScroll', 'MozMousePixelScroll', 'resize', 'touchmove', 'touchend'],
    _instances:[],
    _positionMap: new Set(),
    _topPos:'',
    _topWrapper:''
  }
  static propTypes = {
    data: React.PropTypes.array.isRequired,
    headerAttName: React.PropTypes.string.isRequired,
    itemsAttName: React.PropTypes.string.isRequired,
    events: React.PropTypes.array,
    _instances: React.PropTypes.array,
    _positionMap: React.PropTypes.object,
    _topPos: React.PropTypes.string,
    _topWrapper: React.PropTypes.object
  };
  state = {
    events: this.props.events,
    _instances: this.props._instances,
    _positionMap: this.props._positionMap,
    _topPos: this.props._topPos
  }
  componentDidMount() {
    this.initStickyHeaders();
  }
  componentWillUnmount() {
  }
  componentDidUpdate() {
  }
  refsToArray(ctx, prefix){
    let results = [];
    for (let i=0;;i++){
      let ref = ctx.refs[prefix + '-' + String(i)];
      if (ref) results.push(ref);
      else return results;
    }
  }
  initHeaderPositions() {
    // Retrieve all instance of headers and store position info
    this.props._instances.forEach((k)=>{
      this.props._positionMap.add(new HeaderPosInfo(
          k, 
          k.refs.header.getDOMNode().offsetTop,
          k.refs.header.getDOMNode().offsetHeight
        ));
    });
    let it = this.props._positionMap.values();
    let first = it.next();
    this.props._topPos = first.value.originalPosition;
    this.props._topWrapper = first.value.headerObj;
  }
  initStickyHeaders () {
    this.props._instances = this.refsToArray(this, 'ListHeader');
    this.initHeaderPositions();
    // Register events listeners with the listview div
    this.props.events.forEach(type => {
      if (window.addEventListener) {
        React.findDOMNode(this.refs.listview).addEventListener(type, this.onScroll.bind(this), false);
      } else {
        React.findDOMNode(this.refs.listview).attachEvent('on' + type, this.onScroll.bind(this), false);
      }
    });
  }
  onScroll() {
    // update current header positions and apply fixed positions to the top one
    console.log(1);
    let offsetTop  = React.findDOMNode(this.props._instances[0].refs.header).offsetTop;
  }
render() {
    const { data, headerAttName, itemsAttName } = this.props;
    let _refi = 0;
    let makeRef = () => {
      return 'ListHeader-' + (_refi++);
    };
    return (
      <div ref="listview" style={styles}>
      {
        Object.keys(data).map(k => {
        const header = data[k][headerAttName];
        const items  = data[k][itemsAttName];
          return (
            <ul key={k}>     
              <ListHeader ref={makeRef()} header={header} />
              <ListItems  items={items} />
            </ul>
          );
        })
      }
      </div>
    );
  }
}