Load Data On Demand
In this demo, the chart loads data as you pan it. Once a data block is loaded, it stays in memory to reduce requests to the server.
www.worldweatheronline.com
Feel free to share demo-related thoughts here.
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If you have technical questions, please create a support ticket in the DevExpress Support Center.
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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, °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 { 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"
},
'devextreme/localization.js': {
"esModule": true
}
},
paths: {
'npm:': 'https://unpkg.com/'
},
map: {
'ts': 'npm:plugin-typescript@8.0.0/lib/plugin.js',
'typescript': 'npm:typescript@3.5.3/lib/typescript.js',
'@angular': 'npm:@angular',
'tslib': 'npm:tslib@2.1.0/tslib.js',
'rxjs': 'npm:rxjs@6.4.0',
'rrule': 'npm:rrule@2.6.6/dist/es5/rrule.js',
'luxon': 'npm:luxon@1.26.0/build/global/luxon.min.js',
'es6-object-assign': 'npm:es6-object-assign@1.1.0',
'devextreme': 'npm:devextreme@20.2.6',
'jszip': 'npm:jszip@3.6.0/dist/jszip.min.js',
'devextreme-quill': 'npm:devextreme-quill@0.10.3/dist/dx-quill.min.js',
'devexpress-diagram': 'npm:devexpress-diagram@2.0.18',
'devexpress-gantt': 'npm:devexpress-gantt@2.0.24',
'devextreme-angular': 'npm:devextreme-angular@20.2.6',
'preact': 'npm:preact@10.5.13/dist/preact.js',
'preact/hooks': 'npm:preact@10.5.13/hooks/dist/hooks.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'
}
},
packageConfigPaths: [
"npm:@angular/*/package.json",
"npm:@angular/common/*/package.json",
"npm:rxjs/package.json",
"npm:rxjs/operators/package.json",
"npm:devextreme-angular/*/package.json",
"npm:devextreme-angular/ui/*/package.json",
"npm:devextreme-angular/package.json",
"npm:devexpress-diagram/package.json",
"npm:devexpress-gantt/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/20.2.6/css/dx.common.css" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/20.2.6/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>