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Charts

Load Data On Demand

In this demo, the range area Chart loads data as you pan it. Once the component loads a data block, this data stays in memory to reduce requests to the server. To implement this functionality, do the following:

  1. Configure a data source.

  2. Configure the Chart to support on-demand data loading.

  3. Implement functions that load the data.

    • In this demo, Chart displays daily information. If a user pan the Chart left or right more than half a day, additional data starts to load. The onVisualRangeChanged initiates this procedure.

    • The uploadDataByVisualRange function analyzes the starting and ending points of the visual range and the bounds of already loaded data. If necessary, it calls the getDataFrame function to obtain new data points. Finally, it reloads the DataSource and saves the current visual range.

    • The getDataFrame Ajax request gets the new data frame from the server.

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<dx-chart id="chart" title="Temperature in Toronto (2017)" [dataSource]="chartDataSource" [zoomAndPan]="{ argumentAxis: 'pan' }" > <dxo-scroll-bar [visible]="true"></dxo-scroll-bar> <dxo-argument-axis argumentType="datetime" [visualRangeUpdateMode]="keep" [(visualRange)]="currentVisualRange" [wholeRange]="bounds" > </dxo-argument-axis> <dxi-value-axis name="temperature" [allowDecimals]="false"> <dxo-title text="Temperature, &deg;C"> <dxo-font color="#ff950c"></dxo-font> </dxo-title> <dxo-label> <dxo-font color="#ff950c"></dxo-font> </dxo-label> </dxi-value-axis> <dxi-series color="#ff950c" type="rangeArea" argumentField="date" rangeValue1Field="minTemp" rangeValue2Field="maxTemp" name="Temperature range" > </dxi-series> <dxo-animation [enabled]="false"></dxo-animation> <dxo-loading-indicator backgroundColor="none"> <dxo-font [size]="14"></dxo-font> </dxo-loading-indicator> <dxo-legend [visible]="false"></dxo-legend> </dx-chart>
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 { lastValueFrom } from 'rxjs'; 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 = 43200000; packetsLock = 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.startValue = range.startValue; this._visualRange.endValue = range.endValue; 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) => ({ 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 lastValueFrom( this.httpClient.get(`https://js.devexpress.com/Demos/WidgetsGallery/data/temperatureData${params}`), ); } 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/ window.config = { transpiler: 'ts', typescriptOptions: { module: 'system', emitDecoratorMetadata: true, experimentalDecorators: true, }, meta: { 'typescript': { 'exports': 'ts', }, 'devextreme/localization.js': { 'esModule': true, }, }, paths: { 'npm:': 'https://unpkg.com/', }, map: { 'ts': 'npm:plugin-typescript@4.2.4/lib/plugin.js', 'typescript': 'npm:typescript@4.2.4/lib/typescript.js', '@angular/core': 'npm:@angular/core@12.2.16', '@angular/platform-browser': 'npm:@angular/platform-browser@12.2.16', '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@12.2.16', '@angular/forms': 'npm:@angular/forms@12.2.16', '@angular/common': 'npm:@angular/common@12.2.16', '@angular/compiler': 'npm:@angular/compiler@12.2.16', 'tslib': 'npm:tslib@2.3.1/tslib.js', 'rxjs': 'npm:rxjs@7.5.3/dist/bundles/rxjs.umd.js', 'rxjs/operators': 'npm:rxjs@7.5.3/dist/cjs/operators/index.js', 'rrule': 'npm:rrule@2.6.4/dist/es5/rrule.js', 'luxon': 'npm:luxon@1.28.0/build/global/luxon.min.js', 'es6-object-assign': 'npm:es6-object-assign@1.1.0', 'devextreme': 'npm:devextreme@22.1.5/cjs', 'devextreme/bundles/dx.all': 'npm:devextreme@22.1.5/bundles/dx.all.js', 'jszip': 'npm:jszip@3.7.1/dist/jszip.min.js', 'devextreme-quill': 'npm:devextreme-quill@1.5.16/dist/dx-quill.min.js', 'devexpress-diagram': 'npm:devexpress-diagram@2.1.63', 'devexpress-gantt': 'npm:devexpress-gantt@4.1.32', 'devextreme-angular': 'npm:devextreme-angular@22.1.5', '@devextreme/runtime': 'npm:@devextreme/runtime@3.0.11', 'inferno': 'npm:inferno@7.4.4/dist/inferno.min.js', 'inferno-compat': 'npm:inferno-compat@7.4.11/dist/inferno-compat.min.js', 'inferno-create-element': 'npm:inferno-create-element@7.4.11/dist/inferno-create-element.min.js', 'inferno-dom': 'npm:inferno-dom/dist/inferno-dom.min.js', 'inferno-hydrate': 'npm:inferno-hydrate@7.4.11/dist/inferno-hydrate.min.js', 'inferno-clone-vnode': 'npm:inferno-clone-vnode@7.4.11/dist/inferno-clone-vnode.min.js', 'inferno-create-class': 'npm:inferno-create-class@7.4.11/dist/inferno-create-class.min.js', 'inferno-extras': 'npm:inferno-extras@7.4.11/dist/inferno-extras.min.js', // Prettier 'prettier/standalone': 'npm:prettier@2.7.1/standalone.js', 'prettier/parser-html': 'npm:prettier@2.7.1/parser-html.js', }, packages: { 'app': { main: './app.component.ts', defaultExtension: 'ts', }, 'devextreme': { defaultExtension: 'js', }, 'devextreme/events/utils': { main: 'index', }, 'devextreme/events': { main: 'index', }, 'es6-object-assign': { main: './index.js', defaultExtension: 'js', }, 'rxjs': { defaultExtension: 'js', }, 'rxjs/operators': { defaultExtension: 'js', }, }, packageConfigPaths: [ 'npm:@devextreme/*/package.json', 'npm:@devextreme/runtime@3.0.11/inferno/package.json', 'npm:@angular/*/package.json', 'npm:@angular/common@12.2.16/*/package.json', 'npm:rxjs@7.5.3/package.json', 'npm:rxjs@7.5.3/operators/package.json', 'npm:devextreme-angular@22.1.5/*/package.json', 'npm:devextreme-angular@22.1.5/ui/*/package.json', 'npm:devextreme-angular@22.1.5/package.json', 'npm:devexpress-diagram@2.1.63/package.json', 'npm:devexpress-gantt@4.1.32/package.json', ], }; System.config(window.config);
<!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/22.1.5/css/dx.common.css" /> <link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/22.1.5/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@0.11.4/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>