Initially
If a node is supposed to be selected initially, set its selected field to true. This is a conventional field name defined by the Default Item Template pattern. If another field specifies whether a node is selected or not, assign its name to the selectedExpr option as shown in the following code.
jQuery
var hierarchicalData = [{
name: 'Fruits',
isSelected: true,
items: [
{ name: 'Apples' },
{ name: 'Oranges' }
]
}, {
name: 'Vegetables',
isSelected: true,
items: [
{ name: 'Cucumbers' },
{ name: 'Tomatoes' }
]
}];
$(function() {
$("#treeViewContainer").dxTreeView({
dataSource: hierarchicalData,
keyExpr: 'name',
displayExpr: 'name',
selectedExpr: 'isSelected',
showCheckBoxesMode: 'normal'
});
});Angular
<dx-tree-view
[dataSource]="hierarchicalData"
keyExpr="name"
displayExpr="name"
selectedExpr="isSelected"
showCheckBoxesMode="normal">
</dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
hierarchicalData = [{
name: 'Fruits',
isSelected: true,
items: [
{ name: 'Apples' },
{ name: 'Oranges' }
]
}, {
name: 'Vegetables',
isSelected: true,
items: [
{ name: 'Cucumbers' },
{ name: 'Tomatoes' }
]
}];
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})Using the API
To select or cancel the selection of a node programmatically, call the selectItem(itemElement) or unselectItem(itemElement) method passing the key of the node as a parameter.
jQuery
$("#treeViewContainer").dxTreeView("selectItem", nodeKey);
// $("#treeViewContainer").dxTreeView("unselectItem", nodeKey);Angular
import { ..., 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;
selectNode (key) {
this.treeView.instance.selectItem(key);
}
unselectNode (key) {
this.treeView.instance.unselectItem(key);
}
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})To select or cancel the selection of all nodes programmatically, call the selectAll() or unselectAll() method.
jQuery
$("#treeViewContainer").dxTreeView("selectAll");
// $("#treeViewContainer").dxTreeView("unselectAll");Angular
import { ..., 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;
selectAllNodes () {
this.treeView.instance.selectAll();
}
unselectAllNodes () {
this.treeView.instance.unselectAll();
}
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})User Interaction
If only a single node should be in the selected state at a time, set the selectByClick option to true. In this case, an end user can click a node to select it.
jQuery
$(function() {
$("#treeViewContainer").dxTreeView({
// ...
selectByClick: true
});
});Angular
<dx-tree-view ...
[selectByClick]="true">
</dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
// ...
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})To select several nodes simultaneously, set the showCheckBoxesMode option to "normal". This adds a check box to each node that enables you to select these nodes. You can also set the showCheckBoxesMode option to "selectAll" to allow a user to select all nodes.
jQuery
$(function() {
$("#treeViewContainer").dxTreeView({
// ...
showCheckBoxesMode: 'normal' // or 'selectAll'
});
});Angular
<dx-tree-view ...
showCheckBoxesMode="normal"> <!-- or "selectAll" -->
</dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
// ...
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})Events
The TreeView raises the following selection-related events:
itemSelectionChanged
Raised after a node's selection state changes.selectAllValueChanged
Raised after the "Select All" check box's state changes.
You can handle these events with functions. Assign the handling functions to the onItemSelectionChanged and onSelectAllValueChanged options when you configure the widget if they are going to remain unchanged at runtime.
jQuery
$(function() {
$("#treeViewContainer").dxTreeView({
onItemSelectionChanged: function (e) {
// Handler of the "itemSelectionChanged" event
},
onSelectAllValueChanged: function (e) {
// Handler of the "selectAllValueChanged" event
}
});
});Angular
<dx-tree-view ...
(onItemSelectionChanged)="onItemSelectionChanged($event)"
(onSelectAllValueChanged)="onSelectAllValueChanged($event)>
</dx-tree-view>
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
onItemSelectionChanged (e) {
// Handler of the "itemSelectionChanged" event
}
onSelectAllValueChanged (e) {
// Handler of the "selectAllValueChanged" event
}
}
@NgModule({
imports: [
// ...
DxTreeViewModule
],
// ...
})If you are going to change the event handler at runtime, or if you need to attach several handlers to the event, subscribe to it using the on(eventName, eventHandler) method. This approach is more typical of jQuery.
var itemSelectionChangedHandler1 = function (e) {
// First handler of the "itemSelectionChanged" event
};
var itemSelectionChangedHandler2 = function (e) {
// Second handler of the "itemSelectionChanged" event
};
$("#treeViewContainer").dxTreeView("instance")
.on("itemSelectionChanged", itemSelectionChangedHandler1)
.on("itemSelectionChanged", itemSelectionChangedHandler2);