cjd-parkball/src/components/tree/demo/dynamic.md

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---
category: 2
title: 异步数据加载
title_en: load data asynchronously
---

 zh-CN

点击展开节点，动态加载数据。

 en-US

To load data asynchronously when click to expand a treeNode.

````jsx
import { Tree } from 'parkball';

const TreeNode = Tree.TreeNode;

class Demo extends React.Component {
  state = {
    treeData: [
      { title: 'Expand to load', key: '0' },
      { title: 'Expand to load', key: '1' },
      { title: 'Tree Node', key: '2', isLeaf: true },
    ],
  }

  onLoadData = (treeNode) => {
    return new Promise((resolve) => {
      if (treeNode.props.children) {
        resolve();
        return;
      }
      setTimeout(() => {
        treeNode.props.dataRef.children = [
          { title: 'Child Node', key: `${treeNode.props.eventKey}-0` },
          { title: 'Child Node', key: `${treeNode.props.eventKey}-1` },
        ];
        this.setState({
          treeData: [...this.state.treeData],
        });
        resolve();
      }, 1000);
    });
  }

  renderTreeNodes = (data) => {
    return data.map((item) => {
      if (item.children) {
        return (
          <TreeNode title={item.title} key={item.key} dataRef={item}>
            {this.renderTreeNodes(item.children)}
          </TreeNode>
        );
      }
      return <TreeNode {...item} dataRef={item} />;
    });
  }

  render() {
    return (
      <Tree loadData={this.onLoadData}>
        {this.renderTreeNodes(this.state.treeData)}
      </Tree>
    );
  }
}

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