5.20231.904
wijmo.nav Class TreeView Wijmo API Class

TreeView Class

The TreeView control displays a hierarchical list of TreeNode objects which may contain text, checkboxes, images, or arbitrary HTML content.

A TreeView is typically used to display the headings in a document, the entries in an index, the files and directories on a disk, or any other kind of information that might usefully be displayed as a hierarchy.

After creating a TreeView, you will typically set the following properties:

  1. itemsSource: an array that contains the data to be displayed on the tree.
  2. displayMemberPath: the name of the data item property that contains the text to display on the nodes (defaults to 'header'), and
  3. childItemsPath: the name of the data item property that contains the node's child items (defaults to 'items').

The TreeView control supports the following keyboard commands:

Key CombinationAction
Up/DownSelect the previous/next visible node
LeftCollapse the selected node if it has child nodes, select the parent node otherwise
RightExpand the selected node if it has child nodes
Home/EndSelect the first/last visible nodes
SpaceToggle the checkbox in the current node (see the showCheckboxes property)
Other charactersSearch for nodes that contain the text typed (multi-character auto-search)

The example below builds a simple tree and allows you to see the effect of the TreeView's main properties:

Example

Heirarchy

Constructors

Properties

Methods

Events

Constructors

constructor

  • new TreeView(element: any, options?: any): TreeView
  • Initializes a new instance of the TreeView class.

    Parameters

    • element: any

      The DOM element that hosts the control, or a CSS selector for the host element (e.g. '#theCtrl').

    • Optional options: any

      The JavaScript object containing initialization data for the control.

    Returns TreeView

Properties

allowDragging

allowDragging: boolean

Gets or sets a value that determines whether users can drag and drop nodes within the TreeView.

The default value for this property is false.

autoCollapse

autoCollapse: boolean

Gets or sets a value that determines if sibling nodes should be collapsed when a node is expanded.

The default value for this property is true, because in most cases collapsing nodes that are not in use helps keep the UI clean.

checkOnClick

checkOnClick: boolean

Gets or sets a value that determines whether to toggle checkboxes when the user clicks the node header.

The default value for this property is false, which causes checkboxes to be toggled only when the user clicks the checkbox itself (not the node header).

See also the showCheckboxes property and the checkedItemsChanged event.

checkedItems

checkedItems: any[]

Gets an array containing the items that are currently checked.

The array returned includes only items that have no children. This is because checkboxes in parent items are used to check or uncheck the child items.

See also the showCheckboxes property and the checkedItemsChanged event.

For example:

import { TreeView } from '@grapecity/wijmo.nav';
var treeViewChk = new TreeView('#gsTreeViewChk', {
   displayMemberPath: 'header',
   childItemsPath: 'items',
   showCheckboxes: true,
   itemsSource: items,
   checkedItemsChanged: function (s, e) {
       var items = s.checkedItems,
           msg = '';
       if (items.length) {
           msg = '<p><b>Selected Items:</b></p><ol>\r\n';
           for (var i = 0; i < items.length; i++) {
               msg += '<li>' + items[i].header + '</li>\r\n';
           }
           msg += '</ol>';
       }
       document.getElementById('gsTreeViewChkStatus').innerHTML = msg;
   }
});

checkedMemberPath

checkedMemberPath: string | string[]

Gets or sets the name of the property (or properties) to bind to the node's checked state.

See also the showCheckboxes property and the checkedItemsChanged event.

childItemsPath

childItemsPath: string | string[]

Gets or sets the name of the property (or properties) that contains the child items for each node.

The default value for this property is the string "items".

In most cases, the property that contains the child items is the same for all data items on the tree. In these cases, set the childItemsPath to that name.

In some cases, however, items at different levels use different properties to store their child items. For example, you could have a tree with categories, products, and orders. In that case, you would set the childItemsPath to an array such as this:

// categories have products, products have orders:
tree.childItemsPath = [ 'Products', 'Orders' ];

collapseOnClick

collapseOnClick: boolean

Gets or sets a value that determines whether to collapse expanded nodes when the user clicks the node header.

The default value for this property is false.

When this property is set to false, users have to click the expand/collapse icons to collapse the node. Clicking the node header will select the node if it is not selected, and will start editing the node if it is selected (and if the isReadOnly property is set to false).

See also the expandOnClick property.

collapseWhenDisabled

collapseWhenDisabled: boolean

Gets or sets a value that determines whether nodes should be collapsed when they are disabled.

The default value for this property is true.

displayMemberPath

displayMemberPath: string | string[]

Gets or sets the name of the property (or properties) to use as the visual representation of the nodes.

The default value for this property is the string "header".

In most cases, the property that contains the node text is the same for all data items on the tree. In these cases, set the displayMemberPath to that name.

In some cases, however, items at different levels use different properties to represent them. For example, you could have a tree with categories, products, and orders. In that case, you might set the displayMemberPath to an array such as this:

// categories, products, and orders have different headers:
tree.displayMemberPath = [ 'CategoryName', 'ProductName', 'OrderID' ];

expandOnClick

expandOnClick: boolean

Gets or sets a value that determines whether to expand collapsed nodes when the user clicks the node header.

The default value for this property is true.

When this property is set to false, users have to click the expand/collapse icons to collapse the node. Clicking the node header will select the node if it is not selected, and will start editing the node if it is selected (and if the isReadOnly property is set to false).

See also the collapseOnClick property.

expandOnLoad

expandOnLoad: boolean

Gets or sets a value that determines whether to automatically expand the first node when the tree is loaded.

The default value for this property is true. If you set it to false, all nodes will be initially collapsed.

hostElement

hostElement: HTMLElement

Gets the DOM element that is hosting the control.

imageMemberPath

imageMemberPath: string | string[]

Gets or sets the name of the property (or properties) to use as a source of images for the nodes.

The default value for this property is an empty string, which means no images are added to the nodes.

isAnimated

isAnimated: boolean

Gets or sets a value that indicates whether to use animations when expanding or collapsing nodes.

The default value for this property is true.

isContentHtml

isContentHtml: boolean

Gets or sets a value indicating whether items are bound to plain text or HTML.

The default value for this property is false.

isDisabled

isDisabled: boolean

Gets or sets a value that determines whether the control is disabled.

Disabled controls cannot get mouse or keyboard events.

isReadOnly

isReadOnly: boolean

Gets or sets a value that determines whether users can edit the text in the nodes.

When the isReadOnly property is set to false, users may edit the content of the tree nodes by typing directly into the nodes. The F2 key can also be used to enter edit mode with the whole node content selected.

You may customize the editing behavior using the following methods and events:

Methods: startEditing, finishEditing.

Events: nodeEditStarting, nodeEditStarted, nodeEditEnding, nodeEditEnded.

The default value for this property is true.

isTouching

isTouching: boolean

Gets a value that indicates whether the control is currently handling a touch event.

isUpdating

isUpdating: boolean

Gets a value that indicates whether the control is currently being updated.

itemsSource

itemsSource: any[]

Gets or sets the array that contains the TreeView items.

TreeView #see:itemsSource arrays usually have a hierarchical structure with items that contain child items. There is no fixed limit to the depth of the items.

For example, the array below would generate a tree with three top-level nodes, each with two child nodes:

import { TreeView } from '@grapecity/wijmo.nav';
var tree = new TreeView('#treeView', {
    displayMemberPath: 'header',
    childItemsPath: 'items',
    itemsSource: [
        { header: '1 first', items: [
            { header: '1.1 first child' },
            { header: '1.2 second child' },
        ] },
        { header: '2 second', items: [
            { header: '3.1 first child' },
            { header: '3.2 second child' },
        ] },
        { header: '3 third', items: [
            { header: '3.1 first child' },
            { header: '3.2 second child' },
        ] }
    ]
});

lazyLoadFunction

lazyLoadFunction: ILazyLoad

Gets or sets a function that loads child nodes on demand.

The lazyLoadFunction takes two parameters: the node being expanded and a callback to be invoked when the data becomes available.

The callback function tells the TreeView that the node loading process has been completed. It should always be called, even if there are errors when loading the data.

For example:

import { TreeView } from '@grapecity/wijmo.nav';
var treeViewLazyLoad = new TreeView('#treeViewLazyLoad', {
   displayMemberPath: 'header',
   childItemsPath: 'items',
   itemsSource: [ // start with three lazy-loaded nodes
       { header: 'Lazy Node 1', items: []},
       { header: 'Lazy Node 2', items: [] },
       { header: 'Lazy Node 3', items: [] }
   ],
   lazyLoadFunction: function (node, callback) {
       setTimeout(function () { // simulate http delay
           var result = [ // simulate result
               { header: 'Another lazy node...', items: [] },
               { header: 'A non-lazy node without children' },
               { header: 'A non-lazy node with child nodes', items: [
                 { header: 'hello' },
                 { header: 'world' }
               ]}
           ];
           callback(result); // return result to control
       }, 2500); // simulated 2.5 sec http delay
   }
});

Trees with lazy-loaded nodes have some restrictions: their nodes may not have checkboxes (see the showCheckboxes property) and the collapseToLevel method will not expand collapsed nodes that have not been loaded yet.

nodes

nodes: TreeNode[]

Gets an array of TreeNode objects representing the nodes currently loaded.

rightToLeft

rightToLeft: boolean

Gets a value indicating whether the control is hosted in an element with right-to-left layout.

selectedItem

selectedItem: any

Gets or sets the data item that is currently selected.

selectedNode

selectedNode: TreeNode

Gets or sets the TreeNode that is currently selected.

selectedPath

selectedPath: string[]

Gets an array containing the text of all nodes from the root to the currently selected node.

showCheckboxes

showCheckboxes: boolean

Gets or sets a value that determines whether the TreeView should add checkboxes to nodes and manage their state.

This property can be used only on trees without lazy-loaded nodes (see the lazyLoadFunction property).

See also the checkedItems property and checkedItemsChanged event.

The default value for this property is false.

tabOrder

tabOrder: number

Gets or sets a value of the tabindex attribute associated with the control.

tabindex attribute value can be defined statically for a Wijmo control by specifying it on the control's host HTML element. But this value can't be changed later during application lifecycle, because Wijmo controls have complex structure, and the control may need to propagate this attribute value to its internal element to work properly.

Because of this, to read or change control's tabindex dynamically, you should do it using this property.

totalItemCount

totalItemCount: number

Gets the total number of items in the tree.

Static controlTemplate

controlTemplate: string

Gets or sets the template used to instantiate TreeView controls.

Methods

addChildNode

  • addChildNode(index: number, dataItem: any): TreeNode
  • Adds a child node at a specific position.

    Parameters

    • index: number

      Index of the new child node.

    • dataItem: any

      Data item used to create the new node.

    Returns TreeNode

    The TreeNode that was added.

addEventListener

  • addEventListener(target: EventTarget, type: string, fn: any, capture?: boolean, passive?: boolean): void
  • Adds an event listener to an element owned by this Control.

    The control keeps a list of attached listeners and their handlers, making it easier to remove them when the control is disposed (see the dispose and removeEventListener methods).

    Failing to remove event listeners may cause memory leaks.

    The passive parameter is set to false by default, which means the event handler may call event.preventDefault(). If you are adding passive handlers to touch or wheel events, setting this parameter to true will improve application performance.

    For details on passive event listeners, please see Improving scrolling performance with passive listeners.

    Parameters

    • target: EventTarget

      Target element for the event.

    • type: string

      String that specifies the event.

    • fn: any

      Function to execute when the event occurs.

    • Optional capture: boolean

      Whether the listener should be handled by the control before it is handled by the target element.

    • Optional passive: boolean

      Indicates that the handler will never call preventDefault().

    Returns void

applyTemplate

  • applyTemplate(classNames: string, template: string, parts: Object, namePart?: string): HTMLElement
  • Applies the template to a new instance of a control, and returns the root element.

    This method should be called by constructors of templated controls. Therefore, this method is not available. It is responsible for binding the template parts to the corresponding control members.

    For example, the code below applies a template to an instance of an InputNumber control. The template must contain elements with the 'wj-part' attribute set to 'input', 'btn-inc', and 'btn-dec'. The control members '_tbx', '_btnUp', and '_btnDn' will be assigned references to these elements.

    this.applyTemplate('wj-control wj-inputnumber', templateString, {
      _tbx: 'input',
      _btnUp: 'btn-inc',
      _btnDn: 'btn-dec'
    }, 'input');

    @param classNames Names of classes to add to the control's host element. @param template An HTML string that defines the control template. @param parts A dictionary of part variables and their names. @param namePart Name of the part to be named after the host element. This determines how the control submits data when used in forms.

    Parameters

    • classNames: string
    • template: string
    • parts: Object
    • Optional namePart: string

    Returns HTMLElement

beginUpdate

  • beginUpdate(): void

checkAllItems

  • checkAllItems(check: boolean): void
  • Checks or unchecks all checkboxes on the tree.

    Parameters

    • check: boolean

      Whether to check or uncheck all checkboxes.

    Returns void

collapseToLevel

  • collapseToLevel(level: number): void
  • Collapses all the tree items to a given level.

    This method will typically expand or collapse multiple nodes at once. But it will not perform lazy-loading on any nodes, so collapsed nodes that must be lazy-loaded will not be expanded.

    Parameters

    • level: number

      Maximum node level to show.

    Returns void

containsFocus

  • containsFocus(): boolean
  • Checks whether this control contains the focused element.

    Returns boolean

deferUpdate

  • deferUpdate(fn: Function): void
  • Executes a function within a beginUpdate/endUpdate block.

    The control will not be updated until the function has been executed. This method ensures endUpdate is called even if the function throws an exception.

    Parameters

    • fn: Function

      Function to be executed.

    Returns void

dispose

  • dispose(): void
  • Disposes of the control by removing its association with the host element.

    The dispose method automatically removes any event listeners added with the addEventListener method.

    Calling the dispose method is important in applications that create and remove controls dynamically. Failing to dispose of the controls may cause memory leaks.

    Returns void

endUpdate

  • endUpdate(): void

finishEditing

  • finishEditing(cancel?: boolean): boolean
  • Commits any pending edits and exits edit mode.

    Parameters

    • Optional cancel: boolean

      Whether pending edits should be canceled or committed.

    Returns boolean

    True if the edit operation finished successfully.

focus

  • focus(): void
  • Sets the focus to this control.

    Returns void

getFirstNode

  • getFirstNode(visible?: boolean, enabled?: boolean): TreeNode
  • Gets a reference to the first TreeNode in the TreeView.

    Parameters

    • Optional visible: boolean

      Whether to return only visible nodes (whose ancestors are not collapsed).

    • Optional enabled: boolean

      Whether to return only enabled nodes (whose ancestors are not disabled).

    Returns TreeNode

getLastNode

  • getLastNode(visible?: boolean, enabled?: boolean): TreeNode
  • Gets a reference to the last TreeNode in the TreeView.

    Parameters

    • Optional visible: boolean

      Whether to return only visible nodes (whose ancestors are not collapsed).

    • Optional enabled: boolean

      Whether to return only enabled nodes (whose ancestors are not disabled).

    Returns TreeNode

getNode

  • Gets the TreeNode object representing a given data item.

    Parameters

    • item: any

      The data item to look for.

    Returns TreeNode

getTemplate

  • getTemplate(): string
  • Gets the HTML template used to create instances of the control.

    This method traverses up the class hierarchy to find the nearest ancestor that specifies a control template. For example, if you specify a prototype for the ComboBox control, which does not specify a template, it will override the template defined by the DropDown base class (the nearest ancestor that does specify a template).

    Returns string

hasOwnProperty

  • hasOwnProperty(v: PropertyKey): boolean
  • Determines whether an object has a property with the specified name.

    Parameters

    • v: PropertyKey

      A property name.

    Returns boolean

initialize

  • initialize(options: any): void
  • Initializes the control by copying the properties from a given object.

    This method allows you to initialize controls using plain data objects instead of setting the value of each property in code.

    For example:

    grid.initialize({
      itemsSource: myList,
      autoGenerateColumns: false,
      columns: [
        { binding: 'id', header: 'Code', width: 130 },
        { binding: 'name', header: 'Name', width: 60 }
      ]
    });
    
    // is equivalent to
    grid.itemsSource = myList;
    grid.autoGenerateColumns = false;
    // etc.

    The initialization data is type-checked as it is applied. If the initialization object contains unknown property names or invalid data types, this method will throw.

    Parameters

    • options: any

      Object that contains the initialization data.

    Returns void

invalidate

  • invalidate(fullUpdate?: boolean): void
  • Invalidates the control causing an asynchronous refresh.

    Parameters

    • Optional fullUpdate: boolean

      Whether to update the control layout as well as the content.

    Returns void

isPrototypeOf

  • isPrototypeOf(v: Object): boolean
  • Determines whether an object exists in another object's prototype chain.

    Parameters

    • v: Object

      Another object whose prototype chain is to be checked.

    Returns boolean

loadTree

  • loadTree(preserveOutlineState?: boolean): void
  • Loads the tree using data from the current itemsSource.

    Parameters

    • Optional preserveOutlineState: boolean

      Whether to preserve the outline state when loading the tree data. Defaults to false.

    Returns void

onCheckedItemsChanged

onDragEnd

onDragOver

onDragStart

onDrop

onFormatItem

onGotFocus

onInvalidInput

onIsCheckedChanged

onIsCheckedChanging

onIsCollapsedChanged

onIsCollapsedChanging

onItemClicked

onItemsSourceChanged

onLoadedItems

onLoadingItems

onLostFocus

onNodeEditEnded

onNodeEditEnding

onNodeEditStarted

onNodeEditStarting

onRefreshed

onRefreshing

onSelectedItemChanged

propertyIsEnumerable

  • propertyIsEnumerable(v: PropertyKey): boolean
  • Determines whether a specified property is enumerable.

    Parameters

    • v: PropertyKey

      A property name.

    Returns boolean

refresh

  • refresh(fullUpdate?: boolean): void
  • Overridden to re-populate the tree.

    Parameters

    • Optional fullUpdate: boolean

      Indicates whether to update the control layout as well as the content.

    Returns void

removeEventListener

  • removeEventListener(target?: EventTarget, type?: string, fn?: any, capture?: boolean): number
  • Removes one or more event listeners attached to elements owned by this Control.

    Parameters

    • Optional target: EventTarget

      Target element for the event. If null, removes listeners attached to all targets.

    • Optional type: string

      String that specifies the event. If null, removes listeners attached to all events.

    • Optional fn: any

      Handler to remove. If null, removes all handlers.

    • Optional capture: boolean

      Whether the listener is capturing. If null, removes capturing and non-capturing listeners.

    Returns number

    The number of listeners removed.

startEditing

  • startEditing(node?: TreeNode): boolean
  • Starts editing a given TreeNode.

    Parameters

    • Optional node: TreeNode

      TreeNode to edit. If not provided, the currently selected node is used.

    Returns boolean

    True if the edit operation started successfully.

toLocaleString

  • toLocaleString(): string
  • Returns a date converted to a string using the current locale.

    Returns string

toString

  • toString(): string
  • Returns a string representation of an object.

    Returns string

valueOf

  • valueOf(): Object
  • Returns the primitive value of the specified object.

    Returns Object

Static disposeAll

  • disposeAll(e?: HTMLElement): void
  • Disposes of all Wijmo controls contained in an HTML element.

    Parameters

    • Optional e: HTMLElement

      Container element.

    Returns void

Static getControl

  • getControl(element: any): Control
  • Gets the control that is hosted in a given DOM element.

    Parameters

    • element: any

      The DOM element that hosts the control, or a CSS selector for the host element (e.g. '#theCtrl').

    Returns Control

Static invalidateAll

  • invalidateAll(e?: HTMLElement): void
  • Invalidates all Wijmo controls contained in an HTML element.

    Use this method when your application has dynamic panels that change the control's visibility or dimensions. For example, splitters, accordions, and tab controls usually change the visibility of its content elements. In this case, failing to notify the controls contained in the element may cause them to stop working properly.

    If this happens, you must handle the appropriate event in the dynamic container and call the Control.invalidateAll method so the contained Wijmo controls will update their layout information properly.

    Parameters

    • Optional e: HTMLElement

      Container element. If set to null, all Wijmo controls on the page will be invalidated.

    Returns void

Static refreshAll

  • refreshAll(e?: HTMLElement): void
  • Refreshes all Wijmo controls contained in an HTML element.

    This method is similar to invalidateAll, except the controls are updated immediately rather than after an interval.

    Parameters

    • Optional e: HTMLElement

      Container element. If set to null, all Wijmo controls on the page will be invalidated.

    Returns void

Events

checkedItemsChanged

checkedItemsChanged: Event<TreeView, EventArgs>

Occurs when the value of the checkedItems property changes.

See also the showCheckboxes and checkOnClick properties.

dragEnd

Occurs when the user finishes a drag/drop operation, either by dropping a node into a new location or by canceling the operation with the mouse or keyboard.

dragOver

Occurs while the user drags a node over other nodes on the TreeView.

This event only occurs if the allowDragging property is set to true.

You may prevent drop operations over certain nodes and/or positions by setting the event's cancel parameter to true.

dragStart

Occurs when the user starts dragging a node.

This event only occurs if the allowDragging property is set to true.

You may prevent nodes from being dragged by setting the event's cancel parameter to true.

drop

Occurs when the user drops a on the TreeView.

returns

True if the event was not canceled.

formatItem

Occurs when an element representing a node has been created.

This event can be used to format nodes for display.

The example below uses the formatItem event to add a "new" badge to the right of new items on the tree.

import { TreeView } from '@grapecity/wijmo.nav';
var treeViewFmtItem = new TreeView('#treeViewFmtItem', {
    displayMemberPath: 'header',
    childItemsPath: 'items',
    itemsSource: items,
    formatItem: function (s, e) {
        if (e.dataItem.newItem) {
            let img = wijmo.createElement('<img style="margin-left:6px" src="resources/new.png">');
            e.element.appendChild(img);
        }
    }
});

gotFocus

gotFocus: Event<Control, EventArgs>

Occurs when the control gets the focus.

invalidInput

invalidInput: Event<Control, CancelEventArgs>

Occurs when invalid input is detected.

Invalid input may occur when the user types or pastes a value that cannot be converted to the proper type, or a value that is outside the valid range.

If the event handler cancels the event, the control will retain the invalid content and the focus, so users can correct the error.

If the event is not canceled, the control will ignore the invalid input and will retain the original content.

isCheckedChanged

isCheckedChanged: Event<TreeView, TreeNodeEventArgs>

Occurs after the value of the TreeNode.isChecked property changes.

isCheckedChanging

isCheckedChanging: Event<TreeView, TreeNodeEventArgs>

Occurs before the value of the TreeNode.isChecked property changes.

isCollapsedChanged

isCollapsedChanged: Event<TreeView, TreeNodeEventArgs>

Occurs after the value of the TreeNode.isCollapsed property changes.

isCollapsedChanging

isCollapsedChanging: Event<TreeView, TreeNodeEventArgs>

Occurs before the value of the TreeNode.isCollapsed property changes.

itemClicked

itemClicked: Event<TreeView, EventArgs>

Occurs when the user clicks an item or presses the Enter key and an item is selected.

This event is typically used in navigation trees. Use the selectedItem property to get the item that was clicked.

itemsSourceChanged

itemsSourceChanged: Event<TreeView, EventArgs>

Occurs when the value of the itemsSource property changes.

loadedItems

loadedItems: Event<TreeView, EventArgs>

Occurs after the tree items have been generated.

loadingItems

Occurs before the tree items are generated.

lostFocus

lostFocus: Event<Control, EventArgs>

Occurs when the control loses the focus.

nodeEditEnded

Occurs after a TreeNode has exited edit mode.

nodeEditEnding

nodeEditEnding: Event<TreeView, TreeNodeEventArgs>

Occurs before a TreeNode exits edit mode.

nodeEditStarted

nodeEditStarted: Event<TreeView, TreeNodeEventArgs>

Occurs after a TreeNode has entered edit mode.

nodeEditStarting

nodeEditStarting: Event<TreeView, TreeNodeEventArgs>

Occurs before a TreeNode enters edit mode.

refreshed

refreshed: Event<Control, EventArgs>

Occurs after the control has refreshed its contents.

refreshing

refreshing: Event<Control, EventArgs>

Occurs when the control is about to refresh its contents.

selectedItemChanged

selectedItemChanged: Event<TreeView, EventArgs>

Occurs when the value of the selectedItem property changes.