Initially
If a node is supposed to be expanded initially, set its expanded field to true. If another field specifies whether a node is expanded or collapsed, assign its name to the expandedExpr property as shown in the following code.
jQuery
var hierarchicalData = [{ name: 'Fruits', isExpanded: true, items: [ { name: 'Apples' }, { name: 'Oranges' } ] }, { name: 'Vegetables', isExpanded: true, items: [ { name: 'Cucumbers' }, { name: 'Tomatoes' } ] }]; $(function() { $("#treeViewContainer").dxTreeView({ dataSource: hierarchicalData, keyExpr: 'name', displayExpr: 'name', expandedExpr: 'isExpanded' }); });
Angular
<dx-tree-view [dataSource]="hierarchicalData" keyExpr="name" displayExpr="name" expandedExpr="isExpanded"> </dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular"; // ... export class AppComponent { hierarchicalData = [{ name: 'Fruits', isExpanded: true, items: [ { name: 'Apples' }, { name: 'Oranges' } ] }, { name: 'Vegetables', isExpanded: true, items: [ { name: 'Cucumbers' }, { name: 'Tomatoes' } ] }]; } @NgModule({ imports: [ // ... DxTreeViewModule ], // ... })
Vue
<template> <DxTreeView key-expr="key" display-expr="name" expanded-expr="isExpanded" :items="hierarchicalData" /> </template> <script> import 'devextreme/dist/css/dx.light.css'; import { DxTreeView } from 'devextreme-vue/tree-view'; const hierarchicalData = [{ key: '1', name: 'Fruits', isExpanded: true, items: [ { key: '1_1', name: 'Apples' }, { key: '1_2', name: 'Oranges' } ] }, { key: '2', name: 'Vegetables', isExpanded: true, items: [ { key: '2_1', name: 'Cucumbers' }, { key: '2_2', name: 'Tomatoes' } ] }]; export default { components: { DxTreeView }, data() { return { hierarchicalData }; }, }; </script>
React
import React from 'react'; import 'devextreme/dist/css/dx.light.css'; import TreeView from 'devextreme-react/tree-view'; const hierarchicalData = [{ key: '1', name: 'Fruits', isExpanded: true, items: [ { key: '1_1', name: 'Apples' }, { key: '1_2', name: 'Oranges' } ] }, { key: '2', name: 'Vegetables', isExpanded: true, items: [ { key: '2_1', name: 'Cucumbers' }, { key: '2_2', name: 'Tomatoes' } ] }]; class App extends React.Component { render() { return ( <TreeView keyExpr="key" displayExpr="name" expandedExpr="isExpanded" items={hierarchicalData} /> ); } } export default App;
Using the API
The TreeView provides the following API to expand and collapse nodes:
All nodes
You can use the expandAll() and collapseAll() methods to expand and collapse nodes at once. Note that the expandAll() method expands only the loaded nodes if data is loaded on demand.jQuery
JavaScript$("#treeViewContainer").dxTreeView("expandAll"); // $("#treeViewContainer").dxTreeView("collapseAll");
Angular
TypeScriptimport { ..., ViewChild } from "@angular/core"; import { DxTreeViewModule, DxTreeViewComponent } from "devextreme-angular"; // ... export class AppComponent { @ViewChild(DxTreeViewComponent, { static: false }) treeView: DxTreeViewComponent; // Prior to Angular 8 // @ViewChild(DxTreeViewComponent) treeView: DxTreeViewComponent; expandAllNodes () { this.treeView.instance.expandAll(); } collapseAllNodes () { this.treeView.instance.collapseAll(); } } @NgModule({ imports: [ // ... DxTreeViewModule ], // ... })
Vue
App.vue<template> <DxTreeView :ref="treeViewRef" :items="data" /> </template> <script> import 'devextreme/dist/css/dx.light.css'; import { DxTreeView } from 'devextreme-vue/tree-view'; const treeViewRef = 'treeView'; const data = [ ... ]; export default { components: { DxTreeView }, data() { return { data, treeViewRef }; }, computed: { treeView: function() { return this.$refs[treeViewRef].instance; } }, methods: { expandAllNodes() { this.treeView.expandAll(); }, collapseAllNodes() { this.treeView.collapseAll(); } } }; </script>
React
App.jsimport React from 'react'; import 'devextreme/dist/css/dx.light.css'; import TreeView from 'devextreme-react/tree-view'; const data = [ ... ]; class App extends React.Component { constructor() { super(); this.treeViewRef = React.createRef(); this.expandAllNodes = this.expandAllNodes.bind(this); this.collapseAllNodes = this.collapseAllNodes.bind(this); } render() { return ( <TreeView items={data} ref={this.treeViewRef} /> ); } expandAllNodes() { this.treeView.expandAll(); } collapseAllNodes() { this.treeView.collapseAll(); } get treeView() { return this.treeViewRef.current.instance(); } } export default App;
Individual nodes
Call the expandItem(key) or collapseItem(key) method and pass a node key as an argument:jQuery
JavaScript$("#treeViewContainer").dxTreeView("expandItem", nodeKey); // $("#treeViewContainer").dxTreeView("collapseItem", nodeKey);
Angular
TypeScriptimport { ..., ViewChild } from "@angular/core"; import { DxTreeViewModule, DxTreeViewComponent } from "devextreme-angular"; // ... export class AppComponent { @ViewChild(DxTreeViewComponent, { static: false }) treeView: DxTreeViewComponent; // Prior to Angular 8 // @ViewChild(DxTreeViewComponent) treeView: DxTreeViewComponent; expandNode (key) { this.treeView.instance.expandItem(key); } collapseNode (key) { this.treeView.instance.collapseItem(key); } } @NgModule({ imports: [ // ... DxTreeViewModule ], // ... })
Vue
App.vue<template> <DxTreeView :ref="treeViewRef" :items="data" /> </template> <script> import 'devextreme/dist/css/dx.light.css'; import { DxTreeView } from 'devextreme-vue/tree-view'; const treeViewRef = 'treeView'; const data = [ ... ]; export default { components: { DxTreeView }, data() { return { data, treeViewRef }; }, computed: { treeView: function() { return this.$refs[treeViewRef].instance; } }, methods: { expandNode(key) { this.treeView.expandItem(key); }, collapseNode(key) { this.treeView.collapseItem(key); } } }; </script>
React
App.jsimport React from 'react'; import 'devextreme/dist/css/dx.light.css'; import TreeView from 'devextreme-react/tree-view'; const data = [ ... ]; class App extends React.Component { constructor() { super(); this.treeViewRef = React.createRef(); this.expandNode = this.expandNode.bind(this); this.collapseNode = this.collapseNode.bind(this); } render() { return ( <TreeView items={data} ref={this.treeViewRef} /> ); } expandNode(key) { this.treeView.expandItem(key); } collapseNode(key) { this.treeView.collapseItem(key); } get treeView() { return this.treeViewRef.current.instance(); } } export default App;
Events
To execute certain commands when a node is expanded or collapsed, handle the itemExpanded or itemCollapsed event. Assign event handling functions to the onItemExpanded or onItemCollapsed property when you configure the UI component if these functions are going to remain unchanged.
jQuery
$(function() { $("#treeViewContainer").dxTreeView({ onItemExpanded: function (e) { // Handler of the "itemExpanded" event }, onItemCollapsed: function (e) { // Handler of the "itemCollapsed" event } }); });
Angular
<dx-tree-view ... (onItemExpanded)="onItemExpanded($event)" (onItemCollapsed)="onItemCollapsed($event)"> </dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular"; // ... export class AppComponent { onItemExpanded (e) { // Handler of the "itemExpanded" event } onItemCollapsed (e) { // Handler of the "itemCollapsed" event } } @NgModule({ imports: [ // ... DxTreeViewModule ], // ... })
Vue
<template> <DxTreeView :data-source="data" @item-expanded="onItemExpanded" @item-collapsed="onItemCollapsed" /> </template> <script> import 'devextreme/dist/css/dx.light.css'; import { DxTreeView } from 'devextreme-vue/tree-view'; const data = [ ... ]; export default { components: { DxTreeView }, data() { return { data }; }, methods: { onItemExpanded(e) { // Handler of the 'itemExpanded' event } onItemCollapsed(e) { // Handler of the 'itemCollapsed' event } } }; </script>
React
import React from 'react'; import 'devextreme/dist/css/dx.light.css'; import TreeView from 'devextreme-react/tree-view'; const data = [ ... ]; class App extends React.Component { render() { return ( <TreeView onItemExpanded={this.onItemExpanded} onItemCollapsed={this.onItemCollapsed} dataSource={data} /> ); } onItemExpanded(e) { // Handler of the 'itemExpanded' event } onItemCollapsed(e) { // Handler of the 'itemCollapsed' event } } export default App;
jQuery
If you are going to change event handlers at runtime, or if you need to attach several handlers to a single event, subscribe to the events using the on(eventName, eventHandler) method.
var itemCollapsedEventHandler1 = function (e) { // First handler of the "itemCollapsed" event }; var itemCollapsedEventHandler2 = function (e) { // Second handler of the "itemCollapsed" event }; $("#treeViewContainer").dxTreeView("instance") .on("itemCollapsed", itemCollapsedEventHandler1) .on("itemCollapsed", itemCollapsedEventHandler2);