Load Data On Demand

import { NgModule, Component, ViewChild, enableProdMode } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'; import { HttpClient, HttpClientModule } from '@angular/common/http'; import { DxChartModule, DxChartComponent } from 'devextreme-angular'; import DataSource from 'devextreme/data/data_source'; if(!/localhost/.test(document.location.host)) { enableProdMode(); } @Component({ selector: 'demo-app', templateUrl: 'app/app.component.html', styleUrls: ['app/app.component.css'] }) export class AppComponent { @ViewChild(DxChartComponent, { static: false }) component: DxChartComponent; private _visualRange: any = {}; HALFDAY: number = 43200000; packetsLock: number = 0; chartDataSource: any; bounds: any; constructor(private httpClient: HttpClient) { this.chartDataSource = new DataSource({ store: [], sort: "date", paginate: false }); this.bounds = { startValue: new Date(2017, 0, 1), endValue: new Date(2017, 11, 31) }; this._visualRange = { startValue: new Date(2017, 3, 1), length: { weeks: 2 } }; } get currentVisualRange(): any { return this._visualRange; } set currentVisualRange(range: any) { this._visualRange = range; this.onVisualRangeChanged(); } onVisualRangeChanged() { const items = this.component.instance.getDataSource().items(); if(!items.length || items[0].date - this._visualRange.startValue >= this.HALFDAY || this._visualRange.endValue - items[items.length - 1].date >= this.HALFDAY) { this.uploadDataByVisualRange(); } } uploadDataByVisualRange() { const dataSource = this.component.instance.getDataSource(); const storage = dataSource.items(); const ajaxArgs = { startVisible: this.getDateString(this._visualRange.startValue), endVisible: this.getDateString(this._visualRange.endValue), startBound: this.getDateString(storage.length ? storage[0].date : null), endBound: this.getDateString(storage.length ? storage[storage.length - 1].date : null) }; if(ajaxArgs.startVisible !== ajaxArgs.startBound && ajaxArgs.endVisible !== ajaxArgs.endBound && !this.packetsLock) { this.packetsLock++; this.component.instance.showLoadingIndicator(); this.getDataFrame(ajaxArgs) .then((dataFrame: any) => { this.packetsLock--; dataFrame = dataFrame.map(i => { return { date: new Date(i.Date), minTemp: i.MinTemp, maxTemp: i.MaxTemp }; }); const componentStorage = dataSource.store(); dataFrame.forEach(item => componentStorage.insert(item)); dataSource.reload(); this.onVisualRangeChanged(); }) .catch(error => { this.packetsLock--; dataSource.reload(); }); } } getDataFrame(args: any) { let params = '?'; params += "startVisible=" + args.startVisible; params += "&endVisible=" + args.endVisible; params += "&startBound=" + args.startBound; params += "&endBound=" + args.endBound; return this.httpClient.get('https://js.devexpress.com/Demos/WidgetsGallery/data/temperatureData' + params).toPromise(); } getDateString(dateTime: Date) { return dateTime ? dateTime.toLocaleDateString("en-US") : ""; } } @NgModule({ imports: [ BrowserModule, DxChartModule, HttpClientModule ], declarations: [AppComponent], bootstrap: [AppComponent] }) export class AppModule { } platformBrowserDynamic().bootstrapModule(AppModule);

::ng-deep #chart { height: 440px; }

// In real applications, you should not transpile code in the browser. You can see how to create your own application with Angular and DevExtreme here: // https://js.devexpress.com/Documentation/Guide/Angular_Components/Getting_Started/Create_a_DevExtreme_Application/ System.config({ transpiler: 'ts', typescriptOptions: { module: "system", emitDecoratorMetadata: true, experimentalDecorators: true }, meta: { 'typescript': { "exports": "ts" }, }, paths: { 'npm:': 'https://unpkg.com/' }, map: { 'ts': 'npm:plugin-typescript@8.0.0/lib/plugin.js', 'typescript': 'npm:typescript@3.4.5/lib/typescript.js', '@angular': 'npm:@angular', 'tslib': 'npm:tslib/tslib.js', 'rxjs': 'npm:rxjs', 'devextreme': 'npm:devextreme@20.1', 'jszip': 'npm:jszip@3.1.3/dist/jszip.min.js', 'quill': 'npm:quill@1.3.7/dist/quill.js', 'devexpress-diagram': 'npm:devexpress-diagram@1.0.14', 'devexpress-gantt': 'npm:devexpress-gantt@1.0.7', 'devextreme-angular': 'npm:devextreme-angular@20.1' }, packages: { 'app': { main: './app.component.ts', defaultExtension: 'ts' }, 'devextreme': { defaultExtension: 'js' }, 'devextreme/events/utils': { main: 'index' }, 'devextreme/events': { main: 'index' }, }, packageConfigPaths: [ "npm:*/package.json", "npm:@angular/*/package.json", "npm:@angular/common/*/package.json", "npm:rxjs/operators/package.json", "npm:devextreme-angular@20.1/*/package.json", "npm:devextreme-angular@20.1/ui/*/package.json", ] });

<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>DevExtreme Demo</title> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/20.1.7/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/20.1.7/css/dx.light.css" /> <script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script> <script src="https://unpkg.com/zone.js@0.10.2/dist/zone.js"></script> <script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script> <script src="https://unpkg.com/systemjs@0.21.3/dist/system.js"></script> <script src="config.js"></script> <script> System.import('app').catch(console.error.bind(console)); </script> </head> <body class="dx-viewport"> <div class="demo-container"> <demo-app>Loading...</demo-app> </div> </body> </html>