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.
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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"
},
},
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@1.0.9',
'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/20.1.6/css/dx.common.css" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/20.1.6/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>