---
order: 7
title:
  zh-CN: 滚动加载无限长列表
  en-US: Infinite & virtualized
---

## zh-CN

结合 [react-virtualized](https://github.com/bvaughn/react-virtualized) 实现滚动加载无限长列表，带有虚拟化（[virtualization](https://blog.jscrambler.com/optimizing-react-rendering-through-virtualization/)）功能，能够提高数据量大时候长列表的性能。

`virtualized` 是在大数据列表中应用的一种技术，主要是为了减少不可见区域不必要的渲染从而提高性能，特别是数据量在成千上万条效果尤为明显。[了解更多](https://blog.jscrambler.com/optimizing-react-rendering-through-virtualization/)

## en-US

An example of infinite list & virtualized loading using [react-virtualized](https://github.com/bvaughn/react-virtualized). [Learn more](https://blog.jscrambler.com/optimizing-react-rendering-through-virtualization/)

`Virtualized` rendering is a technique to mount big sets of data. It reduces the amount of rendered DOM nodes by tracking and hiding whatever isn't currently visible.

````jsx
import {
  List, message, Avatar, Spin,
} from 'antd';

import reqwest from 'reqwest';

import WindowScroller from 'react-virtualized/dist/commonjs/WindowScroller';
import AutoSizer from 'react-virtualized/dist/commonjs/AutoSizer';
import VList from 'react-virtualized/dist/commonjs/List';
import InfiniteLoader from 'react-virtualized/dist/commonjs/InfiniteLoader';

const fakeDataUrl = 'https://randomuser.me/api/?results=5&inc=name,gender,email,nat&noinfo';

class VirtualizedExample extends React.Component {
  state = {
    data: [],
    loading: false,
  }

  loadedRowsMap = {}

  componentDidMount() {
    this.fetchData((res) => {
      this.setState({
        data: res.results,
      });
    });
  }

  fetchData = (callback) => {
    reqwest({
      url: fakeDataUrl,
      type: 'json',
      method: 'get',
      contentType: 'application/json',
      success: (res) => {
        callback(res);
      },
    });
  }

  handleInfiniteOnLoad = ({ startIndex, stopIndex }) => {
    let data = this.state.data;
    this.setState({
      loading: true,
    });
    for (let i = startIndex; i <= stopIndex; i++) {
      // 1 means loading
      this.loadedRowsMap[i] = 1;
    }
    if (data.length > 19) {
      message.warning('Virtualized List loaded all');
      this.setState({
        loading: false,
      });
      return;
    }
    this.fetchData((res) => {
      data = data.concat(res.results);
      this.setState({
        data,
        loading: false,
      });
    });
  }

  isRowLoaded = ({ index }) => !!this.loadedRowsMap[index]

  renderItem = ({ index, key, style }) => {
    const { data } = this.state;
    const item = data[index];
    return (
      <List.Item key={key} style={style}>
        <List.Item.Meta
          avatar={<Avatar src="https://zos.alipayobjects.com/rmsportal/ODTLcjxAfvqbxHnVXCYX.png" />}
          title={<a href="https://ant.design">{item.name.last}</a>}
          description={item.email}
        />
        <div>Content</div>
      </List.Item>
    );
  }

  render() {
    const { data } = this.state;
    const vlist = ({
      height, isScrolling, onChildScroll, scrollTop, onRowsRendered, width,
    }) => (
      <VList
        autoHeight
        height={height}
        isScrolling={isScrolling}
        onScroll={onChildScroll}
        overscanRowCount={2}
        rowCount={data.length}
        rowHeight={73}
        rowRenderer={this.renderItem}
        onRowsRendered={onRowsRendered}
        scrollTop={scrollTop}
        width={width}
      />
    );
    const autoSize = ({
      height, isScrolling, onChildScroll, scrollTop, onRowsRendered,
    }) => (
      <AutoSizer disableHeight>
        {({ width }) => vlist({
          height, isScrolling, onChildScroll, scrollTop, onRowsRendered, width,
        })}
      </AutoSizer>
    );
    const infiniteLoader = ({
      height, isScrolling, onChildScroll, scrollTop,
    }) => (
      <InfiniteLoader
        isRowLoaded={this.isRowLoaded}
        loadMoreRows={this.handleInfiniteOnLoad}
        rowCount={data.length}
      >
        {({ onRowsRendered }) => autoSize({
          height, isScrolling, onChildScroll, scrollTop, onRowsRendered,
        })}
      </InfiniteLoader>
    );
    return (
      <List>
        {
          data.length > 0 && (
            <WindowScroller>
              {infiniteLoader}
            </WindowScroller>
          )
        }
        {this.state.loading && <Spin className="demo-loading" />}
      </List>
    );
  }
}

ReactDOM.render(<VirtualizedExample />, mountNode);
````

````css
.demo-loading {
  position: absolute;
  bottom: -40px;
  left: 50%;
}
````