Lazy-Loaded TreeGrid (Vue)

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 Vue.

<template> <div class="container-fluid"> <wj-flex-grid :items-source="data" headers-visibility="Column" child-items-path="children" :group-collapsed-changed="onGroupCollapsedChanged" :initialized="initialGrid"> <wj-flex-grid-column binding="name" header="Customer Name" width="*"></wj-flex-grid-column> <wj-flex-grid-column binding="id" header="ID" align="center" css-class="id-column"></wj-flex-grid-column> </wj-flex-grid> <p> The grid currently has <b id="rowCount" v-html="rowCountText"></b> rows. </p> </div> </template> <script> import "@mescius/wijmo.styles/wijmo.css"; import "bootstrap.css"; import { createApp } from "vue" import * as wjcCore from '@mescius/wijmo'; import { registerGrid } from "@mescius/wijmo.vue2.grid"; import { getData, createNode } from "./data"; let App = { name: "App", data: function () { return { data: getData(), rowCountText: '' } }, mounted: function () { this.grid.collapseGroupsToLevel(0); this._updateRowCount(this.grid); }, methods: { initialGrid(grid) { this.grid = 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.rowCountText = wjcCore.Globalize.format(grid.rows.length, 'n0'); } } }; const app = createApp(App); registerGrid(app) app.mount('#app'); </script> <style> .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; } </style>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS 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/0.21.5/system.src.js" integrity="sha512-skZbMyvYdNoZfLmiGn5ii6KmklM82rYX2uWctBhzaXPxJgiv4XBwJnFGr5k8s+6tE1pcR1nuTKghozJHyzMcoA==" crossorigin="anonymous"></script> <script src="systemjs.config.js"></script> <script> System.import('./src/app.vue'); </script> </head> <body> <div id="app"> </div> </body> </html>
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)]; }
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