最佳答案
获取 div 的偏移量 React 中的顶部位置
我试图在 React 中实现 List 视图。
我试图实现的是存储列表头信息，注册组件和注册滚动事件。
每次当用户滚动窗口时，我想取出存储的 div 并重新计算 offsetTop数据。
现在的问题是，我发现控制台只是打印出初始值(这个值是固定的，从来没有改变过) offsetTop数据在 onscroll函数中从来没有改变过。
有人建议如何从 _instances对象获得最新的 offsetTop？
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>
);
}
}
整个源代码都在 Github 上，你可以从这里克隆和编译它:
