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 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import ReactDOM from 'react-dom/client'; import React, { useRef } from 'react'; import useEvent from 'react-use-event-hook'; import * as wjcCore from '@mescius/wijmo'; import * as wjcGrid from '@mescius/wijmo.react.grid'; import './app.css'; import { createNode, data } from './data'; function App() { const gridRef = useRef(null); const initialGrid = useEvent((grid) => { gridRef.current = grid; gridRef.current.collapseGroupsToLevel(0); updateRowCount(gridRef.current); }); const onGroupCollapsedChanged = useEvent((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 updateRowCount(s); } }); const updateRowCount = (grid) => { const text = wjcCore.Globalize.format(grid.rows.length, 'n0'); const node = document.querySelectorAll('#rowCount')[0]; node.innerHTML = text; }; return (<div className="container-fluid"> <wjcGrid.FlexGrid itemsSource={data} headersVisibility="Column" groupCollapsedChanged={onGroupCollapsedChanged} initialized={initialGrid} childItemsPath="children"> <wjcGrid.FlexGridColumn binding="name" header="Customer Name" width="*"/> <wjcGrid.FlexGridColumn binding="id" header="ID" align="center" css-class="id-column"/> </wjcGrid.FlexGrid> <p> The grid currently has <b id="rowCount"></b> rows. </p> </div>); } const container = document.getElementById('app'); if (container) { const root = ReactDOM.createRoot(container); root.render(<App />); }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo Wijmo FlexGrid Lazy Loading Tree Grid</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- SystemJS --> <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.40/system.src.js" integrity="sha512-G6mEj6h18+m3MvzdviSDfPle/TfH0//cXcB33AKlNR/Rha0yQsKefDZKRTkIZos97HEGq2JMV1RT5ybMoQ3WsQ==" crossorigin="anonymous"></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; }
var nodeId; 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)]; } export const data = getData();
(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', '@mescius/wijmo': 'npm:@mescius/wijmo/index.js', '@mescius/wijmo.input': 'npm:@mescius/wijmo.input/index.js', '@mescius/wijmo.styles': 'npm:@mescius/wijmo.styles', '@mescius/wijmo.cultures': 'npm:@mescius/wijmo.cultures', '@mescius/wijmo.chart': 'npm:@mescius/wijmo.chart/index.js', '@mescius/wijmo.chart.analytics': 'npm:@mescius/wijmo.chart.analytics/index.js', '@mescius/wijmo.chart.animation': 'npm:@mescius/wijmo.chart.animation/index.js', '@mescius/wijmo.chart.annotation': 'npm:@mescius/wijmo.chart.annotation/index.js', '@mescius/wijmo.chart.finance': 'npm:@mescius/wijmo.chart.finance/index.js', '@mescius/wijmo.chart.finance.analytics': 'npm:@mescius/wijmo.chart.finance.analytics/index.js', '@mescius/wijmo.chart.hierarchical': 'npm:@mescius/wijmo.chart.hierarchical/index.js', '@mescius/wijmo.chart.interaction': 'npm:@mescius/wijmo.chart.interaction/index.js', '@mescius/wijmo.chart.radar': 'npm:@mescius/wijmo.chart.radar/index.js', '@mescius/wijmo.chart.render': 'npm:@mescius/wijmo.chart.render/index.js', '@mescius/wijmo.chart.webgl': 'npm:@mescius/wijmo.chart.webgl/index.js', '@mescius/wijmo.chart.map': 'npm:@mescius/wijmo.chart.map/index.js', '@mescius/wijmo.gauge': 'npm:@mescius/wijmo.gauge/index.js', '@mescius/wijmo.grid': 'npm:@mescius/wijmo.grid/index.js', '@mescius/wijmo.grid.detail': 'npm:@mescius/wijmo.grid.detail/index.js', '@mescius/wijmo.grid.filter': 'npm:@mescius/wijmo.grid.filter/index.js', '@mescius/wijmo.grid.search': 'npm:@mescius/wijmo.grid.search/index.js', '@mescius/wijmo.grid.grouppanel': 'npm:@mescius/wijmo.grid.grouppanel/index.js', '@mescius/wijmo.grid.multirow': 'npm:@mescius/wijmo.grid.multirow/index.js', '@mescius/wijmo.grid.transposed': 'npm:@mescius/wijmo.grid.transposed/index.js', '@mescius/wijmo.grid.transposedmultirow': 'npm:@mescius/wijmo.grid.transposedmultirow/index.js', '@mescius/wijmo.grid.pdf': 'npm:@mescius/wijmo.grid.pdf/index.js', '@mescius/wijmo.grid.sheet': 'npm:@mescius/wijmo.grid.sheet/index.js', '@mescius/wijmo.grid.xlsx': 'npm:@mescius/wijmo.grid.xlsx/index.js', '@mescius/wijmo.grid.selector': 'npm:@mescius/wijmo.grid.selector/index.js', '@mescius/wijmo.grid.cellmaker': 'npm:@mescius/wijmo.grid.cellmaker/index.js', '@mescius/wijmo.grid.immutable': 'npm:@mescius/wijmo.grid.immutable/index.js', '@mescius/wijmo.touch': 'npm:@mescius/wijmo.touch/index.js', '@mescius/wijmo.cloud': 'npm:@mescius/wijmo.cloud/index.js', '@mescius/wijmo.nav': 'npm:@mescius/wijmo.nav/index.js', '@mescius/wijmo.odata': 'npm:@mescius/wijmo.odata/index.js', '@mescius/wijmo.olap': 'npm:@mescius/wijmo.olap/index.js', '@mescius/wijmo.rest': 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"npm:react-use-event-hook/dist/esm/useEvent.js", }, // packages tells the System loader how to load when no filename and/or no extension packages: { src: { defaultExtension: 'jsx' }, "node_modules": { defaultExtension: 'js' }, } }); })(this);