Re-loading Lazy-Loaded Nodes (Angular)

By default, lazy-loaded TreeView nodes load their data only once, when the node is expanded for the first time. This sample shows how you can change that behavior for selected nodes causing them to re-load their data whenever they are expanded.

Learn about Wijmo | TreeView Lazy Loading Documentation | TreeView API Reference

This example uses Angular.

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import './styles.css'; // import * as wjCore from '@mescius/wijmo'; import * as wjNav from '@mescius/wijmo.nav'; // import '@angular/compiler'; import { Component, Inject, enableProdMode, ɵresolveComponentResources } from '@angular/core'; import { BrowserModule, bootstrapApplication } from '@angular/platform-browser'; import { WjNavModule } from '@mescius/wijmo.angular2.nav'; import { DataService } from './app.data'; // @Component({ standalone: true, providers: [DataService], imports: [WjNavModule, BrowserModule], selector: 'app-component', templateUrl: 'src/app.component.html', }) export class AppComponent { data: any[]; // constructor(@Inject(DataService) private dataService: DataService) { this.data = dataService.getData(); } // lazyLoadFunction = (node: wjNav.TreeNode, callback: Function) => { setTimeout(() => { let result = this._getLazyData(); callback(result); }, 1000); }; // onIsCollapsedChanging(e: wjNav.TreeNodeEventArgs) { let node = e.node, tree = node.treeView; // if (!node.isCollapsed && node.dataItem.reload) { // remove previous lazy-loaded items from data source node.dataItem.items = []; // // re-bind the tree to remove the old nodes tree.loadTree(); } } // // lazy data (re-loaded when opening nodes) private _getLazyData() { let creationTime = wjCore.Globalize.format(new Date(), 'hh:mm:ss'); // return [ { header: 'Empty Node at: ' + creationTime }, { header: 'Node with child nodes at: ' + creationTime, items: [{ header: 'hello' }, { header: 'world' }], }, { header: 'Lazy node <i>(reload when opening)</i>', items: <any>[], reload: true }, ]; } } // // enableProdMode(); // Resolve resources (templateUrl, styleUrls etc), After resolution all URLs have been converted into `template` strings. ɵresolveComponentResources(fetch).then(() => { // Bootstrap application bootstrapApplication(AppComponent).catch((err) => console.error(err)); });
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>MESCIUS Wijmo TreeView Lazy Re-Loading</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <!-- Polyfills --> <script src="node_modules/core-js/client/shim.min.js"></script> <script src="node_modules/zone.js/fesm2015/zone.min.js"></script> <!-- 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> // workaround to load 'rxjs/operators' from the rxjs bundle System.import('rxjs').then(function (m) { System.set(SystemJS.resolveSync('rxjs/operators'), System.newModule(m.operators)); System.import('./src/app.component'); }); </script> </head> <body> <app-component></app-component> </body> </html>
<div class="container-fluid"> <wj-tree-view #tvLazyLoadOData [itemsSource]="data" [displayMemberPath]="'header'" [childItemsPath]="'items'" [isContentHtml]=true [allowDragging]=true [expandOnClick]=false [autoCollapse]=false [lazyLoadFunction]="lazyLoadFunction" (isCollapsedChanging)="onIsCollapsedChanging($event)"> </wj-tree-view> </div>
import { Injectable } from '@angular/core'; // export class TreeItem { header: string; reload?: boolean; items?: TreeItem[] | any[] } // @Injectable() export class DataService { getData(): TreeItem[] { return [ { header: 'Electronics <i>(reload when opening)</i>', items: [], reload: true }, { header: 'Toys <i>(load once)</i>', items: [] }, { header: 'Home <i>(load once)</i>', items: [] } ]; } }
.wj-treeview { background-color: rgba(0,0,0,.1); padding: 12px; box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23); height: 400px; }
(function (global) { SystemJS.config({ transpiler: './plugin-typescript.js', typescriptOptions: { "target": "ES2022", "module": "system", "emitDecoratorMetadata": true, "experimentalDecorators": true, }, baseURL: 'node_modules/', meta: { 'typescript': { "exports": "ts" }, '*.css': { loader: 'systemjs-plugin-css' }, '*.mjs': { format: 'esm' }, }, paths: { // paths serve as alias 'npm:': '' }, packageConfigPaths: [ '/node_modules/*/package.json', "/node_modules/@angular/*/package.json", "/node_modules/@mescius/*/package.json" ], map: { 'core-js': 'https://cdn.jsdelivr.net/npm/core-js@2.6.12/client/shim.min.js', 'typescript': 'https://cdnjs.cloudflare.com/ajax/libs/typescript/5.2.2/typescript.min.js', "rxjs": "https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.8.1/rxjs.umd.min.js", 'systemjs-plugin-css': 'https://cdn.jsdelivr.net/npm/systemjs-plugin-css@0.1.37/css.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.style': 'npm:@mescius/wijmo.grid.style/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': 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'npm:@mescius/wijmo.angular2.barcode.specialized/index.js', 'bootstrap.css': 'npm:bootstrap/dist/css/bootstrap.min.css', 'jszip': 'https://cdnjs.cloudflare.com/ajax/libs/jszip/3.10.1/jszip.min.js', '@angular/core': 'npm:@angular/core/fesm2022/core.mjs', '@angular/core/primitives/di': 'npm:@angular/core/fesm2022/primitives/di.mjs', '@angular/core/primitives/signals': 'npm:@angular/core/fesm2022/primitives/signals.mjs', '@angular/core/primitives/event-dispatch': 'npm:@angular/core/fesm2022/primitives/event-dispatch.mjs', '@angular/common': 'npm:@angular/common/fesm2022/common.mjs', '@angular/common/http': 'npm:@angular/common/fesm2022/http.mjs', '@angular/compiler': 'npm:@angular/compiler/fesm2022/compiler.mjs', '@angular/platform-browser': 'npm:@angular/platform-browser/fesm2022/platform-browser.mjs', '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/fesm2022/platform-browser-dynamic.mjs', '@angular/http': 'npm:@angular/http/fesm2022/http.mjs', '@angular/router': 'npm:@angular/router/fesm2022/router.mjs', '@angular/forms': 'npm:@angular/forms/fesm2022/forms.mjs', }, // packages tells the System loader how to load when no filename and/or no extension packages: { "./src": { defaultExtension: 'ts' }, "node_modules": { defaultExtension: 'js' }, wijmo: { defaultExtension: 'js', } } }); })(this);