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Load Data on Demand
This example demonstrates how to load data on demand every time a user expands a TreeList node. For this purpose, filtering is delegated to the server, and IDs of expanded nodes are sent to the server with every request for data.
Feel free to share demo-related thoughts here.
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<dx-tree-list
id="treelist"
[dataSource]="dataSource"
[showBorders]="true"
[remoteOperations]="{ filtering: true }"
keyExpr="id"
parentIdExpr="parentId"
hasItemsExpr="hasItems"
rootValue="">
<dxi-column dataField="name"></dxi-column>
<dxi-column dataField="size" [width]="100" [customizeText]="customizeSizeText"></dxi-column>
<dxi-column dataField="createdDate" dataType="date" [width]="150"></dxi-column>
<dxi-column dataField="modifiedDate" dataType="date" [width]="150"></dxi-column>
</dx-tree-list>
import { NgModule, Component, 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 { DxTreeListModule } from 'devextreme-angular';
if(!/localhost/.test(document.location.host)) {
enableProdMode();
}
@Component({
selector: 'demo-app',
templateUrl: 'app/app.component.html',
styleUrls: ['app/app.component.css'],
})
export class AppComponent {
dataSource: any;
constructor(http: HttpClient) {
this.dataSource = {
load: function(loadOptions) {
return http.get("https://js.devexpress.com/Demos/Mvc/api/treeListData?parentIds=" + loadOptions.parentIds)
.toPromise();
}
}
}
customizeSizeText(e) {
if(e.value !== null) {
return Math.ceil(e.value / 1024) + " KB";
}
}
}
@NgModule({
imports: [
BrowserModule,
DxTreeListModule,
HttpClientModule
],
declarations: [AppComponent],
bootstrap: [AppComponent]
})
export class AppModule { }
platformBrowserDynamic().bootstrapModule(AppModule);
::ng-deep #treelist {
max-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@1.25.0/build/global/luxon.min.js',
'es6-object-assign': 'npm:es6-object-assign@1.1.0',
'devextreme': 'npm:devextreme@20.2.5',
'jszip': 'npm:jszip@3.5.0/dist/jszip.min.js',
'devextreme-quill': 'npm:devextreme-quill@0.9.8/dist/dx-quill.min.js',
'devexpress-diagram': 'npm:devexpress-diagram@2.0.11',
'devexpress-gantt': 'npm:devexpress-gantt@2.0.18',
'devextreme-angular': 'npm:devextreme-angular@20.2.5',
'preact': 'npm:preact@10.5.11/dist/preact.js',
'preact/hooks': 'npm:preact@10.5.11/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/20.2.5/css/dx.common.css" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/20.2.5/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@0.10.2/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>