Infinite Scroll in ListBox

This sample shows how you can use the native HTML scroll event to add items to a ListBox when the user scrolls down near the bottom of the list. When the end of the list is near, new items are added to the itemsSource property.

Learn about Input Controls | ListBox API Reference

import 'bootstrap.css'; import '@grapecity/wijmo.styles/wijmo.css'; import './styles.css'; // import * as wjInput from '@grapecity/wijmo.input'; import { getData } from './data'; // document.readyState === 'complete' ? init() : window.onload = init; // function init() { // the ListBox let theListBox = new wjInput.ListBox('#theListBox', { itemsSource: getData() }); // // add elements when the user scrolls to the bottom of the list theListBox.hostElement.addEventListener('scroll', e => { let el = e.target; // // near the bottom? if (el.scrollTop + el.clientHeight > el.scrollHeight - 20) { // // add five elements to the list let arr = theListBox.itemsSource; for (let i = 0; i < 5; i++) { arr.push('item ' + arr.length); } // // refresh the list and keep the scroll top let top = el.scrollTop; theListBox.collectionView.refresh(); el.scrollTop = top; // // show how many items we have let cnt = document.querySelector('#count'); cnt.textContent = `The list now has ${arr.length} items.`; } }); }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>GrapeCity Infinite ListBox</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 class="container-fluid"> <div id="theListBox"></div> <p id="count"> </p> </div> </body> </html>
// get some data export function getData() { let arr = []; for (let i = 0; i < 20; i++) { arr.push('item ' + i); } return arr; }
.wj-listbox { height: 200px; width: 200px; margin-left: 2em; } .wj-listbox-item { line-height: 2.5em; } body { margin-bottom: 24pt; }
(function (global) { System.config({ transpiler: 'plugin-babel', babelOptions: { es2015: 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': 'npm:@grapecity/wijmo.chart.finance.analytics/index.js', '@grapecity/wijmo.chart.hierarchical': 'npm:@grapecity/wijmo.chart.hierarchical/index.js', '@grapecity/wijmo.chart.interaction': 'npm:@grapecity/wijmo.chart.interaction/index.js', '@grapecity/wijmo.chart.radar': 'npm:@grapecity/wijmo.chart.radar/index.js', '@grapecity/wijmo.chart.render': 'npm:@grapecity/wijmo.chart.render/index.js', '@grapecity/wijmo.chart.webgl': 'npm:@grapecity/wijmo.chart.webgl/index.js', '@grapecity/wijmo.gauge': 'npm:@grapecity/wijmo.gauge/index.js', '@grapecity/wijmo.grid': 'npm:@grapecity/wijmo.grid/index.js', '@grapecity/wijmo.grid.detail': 'npm:@grapecity/wijmo.grid.detail/index.js', '@grapecity/wijmo.grid.filter': 'npm:@grapecity/wijmo.grid.filter/index.js', '@grapecity/wijmo.grid.search': 'npm:@grapecity/wijmo.grid.search/index.js', '@grapecity/wijmo.grid.grouppanel': 'npm:@grapecity/wijmo.grid.grouppanel/index.js', '@grapecity/wijmo.grid.multirow': 'npm:@grapecity/wijmo.grid.multirow/index.js', '@grapecity/wijmo.grid.transposed': 'npm:@grapecity/wijmo.grid.transposed/index.js', '@grapecity/wijmo.grid.transposedmultirow': 'npm:@grapecity/wijmo.grid.transposedmultirow/index.js', '@grapecity/wijmo.grid.pdf': 'npm:@grapecity/wijmo.grid.pdf/index.js', '@grapecity/wijmo.grid.sheet': 'npm:@grapecity/wijmo.grid.sheet/index.js', '@grapecity/wijmo.grid.xlsx': 'npm:@grapecity/wijmo.grid.xlsx/index.js', '@grapecity/wijmo.grid.selector': 'npm:@grapecity/wijmo.grid.selector/index.js', '@grapecity/wijmo.grid.cellmaker': 'npm:@grapecity/wijmo.grid.cellmaker/index.js', '@grapecity/wijmo.nav': 'npm:@grapecity/wijmo.nav/index.js', '@grapecity/wijmo.odata': 'npm:@grapecity/wijmo.odata/index.js', '@grapecity/wijmo.olap': 'npm:@grapecity/wijmo.olap/index.js', '@grapecity/wijmo.pdf': 'npm:@grapecity/wijmo.pdf/index.js', '@grapecity/wijmo.pdf.security': 'npm:@grapecity/wijmo.pdf.security/index.js', '@grapecity/wijmo.viewer': 'npm:@grapecity/wijmo.viewer/index.js', '@grapecity/wijmo.xlsx': 'npm:@grapecity/wijmo.xlsx/index.js', '@grapecity/wijmo.undo': 'npm:@grapecity/wijmo.undo/index.js', '@grapecity/wijmo.interop.grid': 'npm:@grapecity/wijmo.interop.grid/index.js', '@grapecity/wijmo.touch': 'npm:@grapecity/wijmo.touch/index.js', '@grapecity/wijmo.cloud': 'npm:@grapecity/wijmo.cloud/index.js', '@grapecity/wijmo.barcode': 'npm:@grapecity/wijmo.barcode/index.js', '@grapecity/wijmo.barcode.common': 'npm:@grapecity/wijmo.barcode.common/index.js', '@grapecity/wijmo.barcode.composite': 'npm:@grapecity/wijmo.barcode.composite/index.js', '@grapecity/wijmo.barcode.specialized': 'npm:@grapecity/wijmo.barcode.specialized/index.js', 'jszip': 'npm:jszip/dist/jszip.js', 'bootstrap.css': 'npm:bootstrap/dist/css/bootstrap.min.css', 'css': 'npm:systemjs-plugin-css/css.js', 'plugin-babel': 'npm:systemjs-plugin-babel/plugin-babel.js', 'systemjs-babel-build':'npm:systemjs-plugin-babel/systemjs-babel-browser.js' }, // packages tells the System loader how to load when no filename and/or no extension packages: { src: { defaultExtension: 'js' }, "node_modules": { defaultExtension: 'js' }, } }); })(this);