Methods

This section describes members used to manipulate the widget.

beginUpdate()

Prevents the widget from refreshing until the endUpdate() method is called.

The beginUpdate() and endUpdate() methods prevent the widget from excessive updates when you are changing multiple widget settings at once. After the beginUpdate() method is called, the widget does not update its UI until the endUpdate() method is called.

See Also

collapseAll()

Collapses all items.

collapseItem(itemData)

Collapses an item with a specific key.

Parameters:
itemData:

Object

The key.

collapseItem(itemElement)

Collapses an item found using its DOM node.

Parameters:
itemElement:

DOM Node

The item's DOM node.

collapseItem(key)

Collapses an item with a specific key.

Parameters:
key: any

The item's key.

defaultOptions(rule)

Specifies the device-dependent default configuration options for this component.

Parameters:
rule:

Object

The component's default device options.

Object structure:
device:

Device

|

Array<Device>

|

Function

Device parameters.
When specifying a function, get information about the current device from the argument. Return true if the options should be applied to the device.

options:

Object

Options to be applied.

defaultOptions is a static method that the widget class supports. The following code demonstrates how to specify default options for all instances of the TreeView widget in an application executed on the desktop.

jQuery
JavaScript
DevExpress.ui.dxTreeView.defaultOptions({ 
    device: { deviceType: "desktop" },
    options: {
        // Here go the TreeView options
    }
});
Angular
TypeScript
import TreeView from "devextreme/ui/tree_view";
// ...
export class AppComponent {
    constructor () {
        TreeView.defaultOptions({
            device: { deviceType: "desktop" },
            options: {
                // Here go the TreeView options
            }
        });
    }
}

dispose()

Disposes of all the resources allocated to the TreeView instance.

The following code disposes of an TreeView instance that corresponds to the element ID (or reference variable in Angular) and removes the element from the DOM:

jQuery
JavaScript
$("#myTreeView").dxTreeView("dispose");
$("#myTreeView").remove();
Angular
HTML
<dx-tree-view #treeViewVar id="myTreeView"></dx-tree-view>
TypeScript
import { ..., ViewChild } from "@angular/core";
import { DxTreeViewComponent } from "devextreme-angular";
// ...
export class AppComponent {
    @ViewChild("treeViewVar") treeView: DxTreeViewComponent;

    removeTreeView (e) {
        this.treeView.instance.dispose();
        document.getElementById("myTreeView").remove();
    }
}

element()

Gets the root widget element.

Return Value:

Element (jQuery or HTML)

An HTML element or a jQuery element when you use jQuery.

See Also

endUpdate()

Refreshes the widget after a call of the beginUpdate() method.

Main article: beginUpdate()

See Also

expandAll()

Expands all items. If you load items on demand, this method expands only the loaded items.

expandItem(itemData)

Expands an item found using its data object.

Parameters:
itemData:

Object

The item's data object.

expandItem(itemElement)

Expands an item found using its DOM node.

Parameters:
itemElement:

DOM Node

The item's DOM node.

expandItem(key)

Expands an item with a specific key.

Parameters:
key: any

The item's key.

focus()

Sets focus on the widget.

See Also

getDataSource()

Gets the DataSource instance.

Return Value:

DataSource

See Also

getInstance(element)

Gets the instance of a widget found using its DOM node.

Parameters:
element:

DOM Node

|

jQuery

The widget's container.

Return Value:

Object

The widget's instance.

getInstance is a static method that the widget class supports. The following code demonstrates how to get the TreeView instance found in an element with the myTreeView ID:

// Modular approach
import TreeView from "devextreme/ui/tree_view";
...
let element = document.getElementById("myTreeView");
let instance = TreeView.getInstance(element) as TreeView;

// Non-modular approach
let element = document.getElementById("myTreeView");
let instance = DevExpress.ui.dxTreeView.getInstance(element);
See Also

getNodes()

Gets all nodes.

Return Value:

Array<TreeView Node>

All nodes. Their structure is described in the Node section.

instance()

Gets the widget's instance. Use it to access other methods of the widget.

Return Value:

TreeView

This widget's instance.

See Also

off(eventName)

Detaches all event handlers from a single event.

Parameters:
eventName:

String

The event's name.

Return Value:

TreeView

The object for which this method is called.

See Also

off(eventName, eventHandler)

Detaches a particular event handler from a single event.

Parameters:
eventName:

String

The event's name.

eventHandler:

Function

The event's handler.

Return Value:

TreeView

The object for which this method is called.

See Also

on(eventName, eventHandler)

Subscribes to an event.

Parameters:
eventName:

String

The event's name.

eventHandler:

Function

The event's handler.

Return Value:

TreeView

The object for which this method is called.

Use this method to subscribe to one of the events listed in the Events section.

See Also

on(events)

Subscribes to events.

Parameters:
events:

Object

Events with their handlers: { "eventName1": handler1, "eventName2": handler2, ...}

Return Value:

TreeView

The object for which this method is called.

Use this method to subscribe to several events with one method call. Available events are listed in the Events section.

See Also

option()

Gets all widget options.

Return Value:

Object

The widget's options.

option(optionName)

Gets the value of a single option.

Parameters:
optionName:

String

The option's name or full path.

Return Value: any

This option's value.

option(optionName, optionValue)

Updates the value of a single option.

Parameters:
optionName:

String

The option's name or full path.

optionValue: any

This option's new value.

option(options)

Updates the values of several options.

Parameters:
options:

Object

Options with their new values.

registerKeyHandler(key, handler)

Registers a handler to be executed when a user presses a specific key.

Parameters:
key:

String

A key.

handler:

Function

A handler. Accepts the keydown event as the argument. It is a dxEvent or a jQuery.Event when you use jQuery.

The key argument accepts one of the following values:

  • "backspace"
  • "tab"
  • "enter"
  • "escape"
  • "pageUp"
  • "pageDown"
  • "end"
  • "home"
  • "leftArrow"
  • "upArrow"
  • "rightArrow"
  • "downArrow"
  • "del"
  • "space"
  • "F"
  • "A"
  • "asterisk"
  • "minus"

A custom handler for a key cancels the default handler for this key.

See Also

repaint()

Repaints the widget. Call it if you made modifications that changed the widget's state to invalid.

See Also

selectAll()

Selects all items.

selectItem(itemData)

Selects an item found using its data object.

Parameters:
itemData:

Object

The item's data object.

selectItem(itemElement)

Selects an item found using its DOM node.

Parameters:
itemElement:

DOM Node

The item's DOM node.

selectItem(key)

Selects an item with a specific key.

Parameters:
key: any

The item's key.

unselectAll()

Cancels the selection of all items.

unselectItem(itemData)

Cancels the selection of an item found using its data object.

Parameters:
itemData:

Object

The item's data object.

unselectItem(itemElement)

Cancels the selection of an item found using its DOM node.

Parameters:
itemElement:

DOM Node

The item's DOM node.

unselectItem(key)

Cancels the selection of an item with a specific key.

Parameters:
key: any

The item's key.

updateDimensions()

Updates the tree view scrollbars according to the current size of the widget content.

Return Value:

Promise<void> (jQuery or native)

A Promise that is resolved if the widget is updated and rejected otherwise. It is a native Promise or a jQuery.Promise when you use jQuery.