Virtualization

The sample below uses the viewRange property to implement a simple type of 'infinite scrolling'. When the user scrolls to the bottom of the grid, the code adds items to the grid's itemsSource. If you inspect the DOM, you will notice that no matter how large the itemsSource gets, the number of DOM elements remains constant. The data is 'virtualized'.

import 'bootstrap.css'; import '@grapecity/wijmo.styles/wijmo.css'; import './styles.css'; import * as wjGrid from '@grapecity/wijmo.grid'; import { getData } from './data'; // document.readyState === 'complete' ? init() : window.onload = init; // function init() { // // start with a small data set var data = getData(100); // // initialize the grid var rowCount = document.getElementById('rowCount'); var cellCount = document.getElementById('cellCount'); var theGrid = new wjGrid.FlexGrid('#theGrid', { itemsSource: data, updatedView: function (s, e) { rowCount.textContent = s.rows.length; cellCount.textContent = s.hostElement.querySelectorAll('.wj-cell').length; }, scrollPositionChanged: function (s, e) { // // if we're close to the bottom, add 20 items if (s.viewRange.bottomRow >= s.rows.length - 1) { let view = s.collectionView; let index = view.currentPosition; // keep position in case the view is sorted addData(data, 20); view.refresh(); view.currentPosition = index; } } }); // // add random data to an array function addData(data, cnt) { var more = getData(cnt, data.length); for (var i = 0; i < more.length; i++) { data.push(more[i]); } } }
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <title>GrapeCity Wijmo FlexGrid Scroll Virtualization</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="theGrid"></div> <p> The grid now has <span id='rowCount'></span> rows and <span id='cellCount'></span> cell elements.</p> </div> </body> </html>
// get an array with random data export function getData(cnt, start) { var data = []; var countries = 'USA,Germany,UK,Japan,Italy,Greece'.split(','); if (!start) start = 0; for (var i = 0; i < cnt; i++) { data.push({ id: i + start, country: countries[i % countries.length], date: new Date(2014, i % 12, i % 28), amount: Math.random() * 10000, active: i % 4 === 0 }); } return data; }
.wj-flexgrid { height: 250px; } #rowCount, #cellCount { font-weight: bold; } 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.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.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', '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);