Lazy-Loaded TreeGrid (React)

In the TreeGrid below, collapsed nodes have a single dummy child. When a node is expanded, more nodes are loaded on demand. This is a common pattern known as 'lazy-loading', and is done by utilizing the groupCollapsedChanged event.

Learn about TreeGrid | Lazy-Loaded Trees Documentation | FlexGrid API Reference

This example uses React.

import "@grapecity/wijmo.styles/wijmo.css"; import "bootstrap.css"; import "./app.css"; // import * as React from 'react'; import * as ReactDOM from 'react-dom/client'; // import * as wjcCore from "@grapecity/wijmo"; import * as wjcGrid from "@grapecity/wijmo.react.grid"; import { createNode, getData } from "./data"; class App extends React.Component { constructor(props) { super(props); this.state = { data: getData(), rowCountText: '' }; } render() { return <div className="container-fluid"> <wjcGrid.FlexGrid itemsSource={this.state.data} headersVisibility="Column" groupCollapsedChanged={this.onGroupCollapsedChanged.bind(this)} initialized={this.initialGrid.bind(this)} childItemsPath="children"> <wjcGrid.FlexGridColumn binding="name" header="Customer Name" width="*"></wjcGrid.FlexGridColumn> <wjcGrid.FlexGridColumn binding="id" header="ID" align="center" css-class="id-column"></wjcGrid.FlexGridColumn> </wjcGrid.FlexGrid> <p> The grid currently has <b id="rowCount"></b> rows. </p> </div>; } initialGrid(grid) { this.grid = grid; this.grid.collapseGroupsToLevel(0); this._updateRowCount(this.grid); } onGroupCollapsedChanged(s, e) { let row = s.rows[e.row], item = row.dataItem; // did we just expand a node with a dummy child? if (!row.isCollapsed && item.children.length == 1 && item.children[0].name == '') { // can't lazy load while updating rows if (s.rows.isUpdating) { row.isCollapsed = true; return; } // replace the dummy child with actual nodes item.children.length = 0; let cnt = Math.round(Math.random() * 5) + 1; for (let i = 0; i < cnt; i++) { let node = createNode(); item.children.push(node); } // refresh the view s.collectionView.refresh(); // collapse the new item's child items for (let i = row.index + 1; i < s.rows.length; i++) { let childRow = s.rows[i]; if (childRow.level <= row.level) { break; } childRow.isCollapsed = true; } // update row count this._updateRowCount(s); } } _updateRowCount(grid) { this.setState({ rowCountText: wjcCore.Globalize.format(grid.rows.length, 'n0') }, () => { const node = document.querySelectorAll('#rowCount')[0]; node.innerHTML = this.state.rowCountText; }); } } setTimeout(() => { const container = document.getElementById('app'); if (container) { const root = ReactDOM.createRoot(container); root.render(<App />); } }, 100);
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>GrapeCity Wijmo FlexGrid Lazy Loading Tree Grid</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="node_modules/systemjs/dist/system.src.js"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app'); </script> </head> <body> <div id="app"></div> </body> </html>
.wj-flexgrid { max-height: 300px; margin: 12px; } .wj-flexgrid .wj-cell { padding: 8px; } .wj-flexgrid .wj-group:not(.wj-state-selected):not(.wj-state-multi-selected) { background-color: white; } .id-column { font-style: italic; } document { margin-bottom: 48pt; }
var nodeId; export function getData() { var tree = []; tree.push(createNode()); tree.push(createNode()); return tree; } export function createNode(dummy) { var first = 'Al,Bob,Cal,Dan,Ed,Fred,Greg,Hal,Ian,Jack,Karl,Lou,Moe,Nate,Oleg,Paul,Quincy,Rod,Sue,Uwe,Vic,Walt,Xiu,Yuri,Zack'.split(','), last = 'Adams,Baum,Cole,Dell,Evans,Fell,Green,Hill,Isman,Jones,Krup,Lee,Monk,Nye,Opus,Pitt,Quaid,Riems,Stark,Trell,Unger,Voss,Wang,Xie,Zalm'.split(','), name = dummy ? '' : getOneOf(first) + ' ' + getOneOf(last), children = []; if (!dummy) { children.push(createNode(true)); } if (nodeId == null) nodeId = 0; return { id: nodeId++, name: name, children: children }; } function getOneOf(arr) { return arr[Math.floor(Math.random() * arr.length)]; }
(function (global) { System.config({ transpiler: 'plugin-babel', babelOptions: { es2015: true, react: true }, meta: { '*.css': { loader: 'css' } }, paths: { // paths serve as alias 'npm:': 'node_modules/' }, // map tells the System loader where to look for things map: { 'jszip': 'npm:jszip/dist/jszip.js', '@grapecity/wijmo': 'npm:@grapecity/wijmo/index.js', '@grapecity/wijmo.input': 'npm:@grapecity/wijmo.input/index.js', '@grapecity/wijmo.styles': 'npm:@grapecity/wijmo.styles', '@grapecity/wijmo.cultures': 'npm:@grapecity/wijmo.cultures', '@grapecity/wijmo.chart': 'npm:@grapecity/wijmo.chart/index.js', '@grapecity/wijmo.chart.analytics': 'npm:@grapecity/wijmo.chart.analytics/index.js', '@grapecity/wijmo.chart.animation': 'npm:@grapecity/wijmo.chart.animation/index.js', '@grapecity/wijmo.chart.annotation': 'npm:@grapecity/wijmo.chart.annotation/index.js', '@grapecity/wijmo.chart.finance': 'npm:@grapecity/wijmo.chart.finance/index.js', '@grapecity/wijmo.chart.finance.analytics': 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