グリッド:無限スクロール (React)

FlexGridは、JavaScriptデータオブジェクトをユーザーが操作できるDOM要素に変換します。多くの場合、データは何千もの項目を含む大きな配列で構成されています。これらの項目のそれぞれにDOM要素を作成すると、ページサイズが大きくなり、動作が遅くなってしまいます。仮想化は、データのどの部分が表示されているかを追跡し、その部分のみを描画する機能です。これにより、ドキュメントツリー内のDOM要素の数が減少し、パフォーマンスが大幅に向上します。FlexGridは、viewRangeプロパティを使用してデータを表示する部分を公開します。ユーザーが画面のサイズを変更したり、グリッドをスクロールすると、viewRangeが更新され、グリッドはその子DOM要素を更新します。

このサンプルはReactを使用しています。

import 'bootstrap.css'; import '@mescius/wijmo.styles/wijmo.css'; import ReactDOM from 'react-dom/client'; import React, { useState } from 'react'; import useEvent from 'react-use-event-hook'; import * as wjGrid from '@mescius/wijmo.react.grid'; import './app.css'; import { data, getData } from './data'; function App() { const [rowCount, setRowCount] = useState(''); const [cellCount, setCellCount] = useState(''); const flexInitialized = useEvent((flexgrid) => { setRowCount(flexgrid.rows.length.toString()); setCellCount(flexgrid.hostElement.querySelectorAll(".wj-cell").length.toString()); flexgrid.updatedView.addHandler(() => { setRowCount(flexgrid.rows.length.toString()); setCellCount(flexgrid.hostElement.querySelectorAll(".wj-cell").length.toString()); }); flexgrid.scrollPositionChanged.addHandler((s) => { // 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; } }); }); const addData = useEvent((data, cnt) => { let more = getData(cnt, data.length); for (let i = 0; i < more.length; i++) { data.push(more[i]); } }); return (<div className="container-fluid"> <wjGrid.FlexGrid initialized={flexInitialized} itemsSource={data}> <wjGrid.FlexGridColumn binding="id" header="ID" width={80}></wjGrid.FlexGridColumn> <wjGrid.FlexGridColumn binding="country" header="国"></wjGrid.FlexGridColumn> <wjGrid.FlexGridColumn binding="date" header="日付"></wjGrid.FlexGridColumn> <wjGrid.FlexGridColumn binding="amount" header="金額" width={80}></wjGrid.FlexGridColumn> <wjGrid.FlexGridColumn binding="active" header="有効"></wjGrid.FlexGridColumn> </wjGrid.FlexGrid> <p> グリッドには <span id="rowCount">{rowCount}</span> {' '}行と<span id="cellCount">{cellCount}</span>個のセル要素が含まれます。 </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 Virtualization</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 { height: 250px; margin: 6px 0px; } #rowCount, #cellCount { font-weight: bold; }
export function getData(cnt, start) { let data = []; let countries = 'アメリカ,ドイツ,イギリス,日本,イタリア,ギリシャ'.split(','); if (start == null) { start = 0; } for (let 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; } export const data = getData(100);
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'systemjs-babel-build':'npm:systemjs-plugin-babel/systemjs-babel-browser.js', "react-use-event-hook": "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);