Version: 2023.2
LanguageEnglish
  • C#

TreeView

class in UnityEngine.UIElements

/

Inherits from:UIElements.BaseTreeView

/

Implemented in:UnityEngine.UIElementsModule

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Description

A TreeView is a vertically scrollable area that links to, and displays, a list of items organized in a tree.

A TreeView is a ScrollView with additional logic to display a tree of vertically-arranged VisualElements. Each VisualElement in the tree is bound to a corresponding element in a data-source list. The data-source list can contain elements of any type. TreeViewItemData_1

The logic required to create VisualElements, and to bind them to or unbind them from the data source, varies depending on the intended result. It's up to you to implement logic that is appropriate to your use case. For the ListView to function correctly, you must supply at least the following:

- BaseVerticalCollectionView.fixedItemHeight

It is also recommended to supply the following for more complex items:

The TreeView creates VisualElements for the visible items, and supports binding many more. As the user scrolls, the TreeView recycles VisualElements and re-binds them to new data items. For more information, refer to UXML element TreeView.

Properties

bindItem Callback for binding a data item to the visual element.
destroyItem Callback invoked when a VisualElement created via makeItem is no longer needed and will be destroyed.
itemTemplate A UXML template that constructs each recycled and rebound element within the tree. This template is designed to replace the makeItem definition.
makeItem Callback for constructing the VisualElement that is the template for each recycled and re-bound element in the list.
unbindItem Callback for unbinding a data item from the VisualElement.
viewController The view controller for this view, cast as a TreeViewController.

Constructors

TreeView Creates a TreeView with all default properties.

Inherited Members

Static Properties

itemContentContainerUssClassName The USS class name for TreeView item container elements.
itemIndentUssClassName The USS class name for TreeView indent element.
itemToggleUssClassName The USS class name for TreeView item toggle elements.
itemUssClassName The USS class name for TreeView item elements.
ussClassName The USS class name for TreeView elements.
borderUssClassName The USS class name for BaseVerticalCollectionView elements with a border.
dragHoverBarUssClassName The USS class name of the drag hover bar.
dragHoverMarkerUssClassName The USS class name of the drag hover circular marker used to indicate depth.
itemAlternativeBackgroundUssClassName The USS class name for odd rows in the BaseVerticalCollectionView.
itemDragHoverUssClassName The USS class name applied to an item element on drag hover.
itemSelectedVariantUssClassName The USS class name of selected item elements in the BaseVerticalCollectionView.
listScrollViewUssClassName The USS class name of the scroll view in the BaseVerticalCollectionView.
disabledUssClassName USS class name of local disabled elements.

Properties

autoExpand When true, items are automatically expanded when added to the TreeView.
itemsSource Access to the itemsSource. For a TreeView, the source contains the items wrappers.
viewController The view controller for this view, cast as a BaseTreeViewController.
contentContainer Returns the content container for the BaseVerticalCollectionView. Because the BaseVerticalCollectionView control automatically manages its content, this always returns null.
fixedItemHeight The height of a single item in the list, in pixels.
horizontalScrollingEnabled This property controls whether the collection view shows a horizontal scroll bar when its content does not fit in the visible area.
reorderable Gets or sets a value that indicates whether the user can drag list items to reorder them.
selectedIndex Returns or sets the selected item's index in the data source. If multiple items are selected, returns the first selected item's index. If multiple items are provided, sets them all as selected.
selectedIndices Returns the indices of selected items in the data source. Always returns an enumerable, even if no item is selected, or a single item is selected.
selectedItem Returns the selected item from the data source. If multiple items are selected, returns the first selected item.
selectedItems Returns the selected items from the data source. Always returns an enumerable, even if no item is selected, or a single item is selected.
selectionType Controls the selection type.
showAlternatingRowBackgrounds This property controls whether the background colors of collection view rows alternate. Takes a value from the AlternatingRowBackground enum.
showBorder Enable this property to display a border around the collection view.
virtualizationMethod The virtualization method to use for this collection when a scroll bar is visible. Takes a value from the CollectionVirtualizationMethod enum.
binding Binding object that will be updated.
bindingPath Path of the target property to be bound.
canGrabFocus Return true if the element can be focused.
delegatesFocus Whether the element should delegate the focus to its children.
focusable True if the element can be focused.
focusController Return the focus controller for this element.
tabIndex An integer used to sort focusables in the focus ring. Must be greater than or equal to zero.
childCount Number of child elements in this object's contentContainer.
contentRect The rectangle of the content area of the element, in the local space of the element.
customStyle Returns the custom style properties accessor for this element.
dataSource Assigns a data source to this VisualElement which overrides any inherited data source. This data source is inherited by all children.
dataSourcePath Path from the data source to the value.
dataSourceType The possible type of data source assignable to this VisualElement. This information is only used by the UI Builder as a hint to provide some completion to the data source path field when the effective data source cannot be specified at design time.
enabledInHierarchy Returns true if the VisualElement is enabled in its own hierarchy.
enabledSelf Returns true if the VisualElement is enabled locally.
experimental Returns the UIElements experimental interfaces.
generateVisualContent Called when the VisualElement visual contents need to be (re)generated.
hierarchy Access to this element physical hierarchy
languageDirection Indicates the directionality of the element's text. The value will propagate to the element's children.
layout The position and size of the VisualElement relative to its parent, as computed by the layout system.
localBound Returns a Rect representing the Axis-aligned Bounding Box (AABB) after applying the transform, but before applying the layout translation.
name The name of this VisualElement.
paddingRect The rectangle of the padding area of the element, in the local space of the element.
panel The panel onto which this VisualElement is attached.
parent The parent of this VisualElement.
pickingMode Determines if this element can be pick during mouseEvents or IPanel.Pick queries.
resolvedStyle Returns the VisualElement resolved style values.
schedule Retrieves this VisualElement's IVisualElementScheduler
style Sets the VisualElement style values.
styleSheets Returns a VisualElementStyleSheetSet that manipulates style sheets attached to this element.
this[int] Retrieves the child element at a specific index.
tooltip Text to display inside an information box after the user hovers the element for a small amount of time. This is only supported in the Editor UI.
transform Returns a transform object for this VisualElement. ITransform
usageHints A combination of hint values that specify high-level intended usage patterns for the VisualElement. This property can only be set when the VisualElement is not yet part of a Panel. Once part of a Panel, this property becomes effectively read-only, and attempts to change it will throw an exception. The specification of proper UsageHints drives the system to make better decisions on how to process or accelerate certain operations based on the anticipated usage pattern. Note that those hints do not affect behavioral or visual results, but only affect the overall performance of the panel and the elements within. It's advised to always consider specifying the proper UsageHints, but keep in mind that some UsageHints might be internally ignored under certain conditions (e.g. due to hardware limitations on the target platform).
userData This property can be used to associate application-specific user data with this VisualElement.
viewDataKey Used for view data persistence, such as tree expanded states, scroll position, or zoom level.
visible Indicates whether or not this element should be rendered.
visualTreeAssetSource Stores the asset reference, if the generated element is cloned from a VisualTreeAsset.
worldBound Returns a Rect representing the Axis-aligned Bounding Box (AABB) after applying the world transform.
worldTransform Returns a matrix that cumulates the following operations (in order): -Local Scaling -Local Rotation -Local Translation -Layout Translation -Parent worldTransform (recursive definition - consider identity when there is no parent)

Public Methods

AddItem Adds an item to the existing tree.
AddToSelectionById Adds an item to the current selection by id.
CollapseAll Collapses all TreeView items, including children.
CollapseItem Collapses the specified TreeView item.
ExpandAll Expands all TreeView items, including children.
ExpandItem Expands the specified TreeView item.
ExpandRootItems Expands all root TreeView items.
GetChildrenIdsForIndex Gets children identifiers for the specified TreeView item.
GetIdForIndex Gets the specified TreeView item's identifier.
GetItemDataForId Gets data for the specified TreeView item id.
GetItemDataForIndex Gets data for the specified TreeView item index.
GetParentIdForIndex Gets the specified TreeView item's parent identifier.
GetRootIds Gets the root item identifiers.
GetSelectedItems Gets tree data for the selected item indices.
GetTreeCount Gets the TreeView's total number of items.
IsExpanded Returns true if the specified TreeView item is expanded, false otherwise.
RemoveFromSelectionById Removes an item from the current selection by id.
SetRootItems Sets the root items to use with the default tree view controller.
SetSelectionById Sets the currently selected item by id.
SetSelectionByIdWithoutNotify Sets a collection of selected items by id, without triggering a selection change callback.
SetViewController Assigns the view controller for this view and registers all events required for it to function properly.
TryRemoveItem Removes an item of the tree if it can find it.
AddToSelection Adds an item to the collection of selected items.
ClearSelection Deselects any selected items.
GetRootElementForId Gets the root element of the specified collection view item.
GetRootElementForIndex Gets the root element of the specified collection view item.
Rebuild Clears the collection view, recreates all visible visual elements, and rebinds all items.
RefreshItem Rebinds a single item if it is currently visible in the collection view.
RefreshItems Rebinds all items currently visible.
RemoveFromSelection Removes an item from the collection of selected items.
ScrollTo Scrolls to a specific VisualElement.
ScrollToItem Scrolls to a specific item index and makes it visible.
ScrollToItemById Scrolls to a specific item id and makes it visible.
SetSelection Sets the currently selected item.
SetSelectionWithoutNotify Sets a collection of selected items without triggering a selection change callback.
HasBubbleUpHandlers Return true if event handlers for the event propagation BubbleUp phase have been attached on this object.
HasTrickleDownHandlers Returns true if event handlers, for the event propagation TrickleDown phase, are attached to this object.
RegisterCallback Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect.
RegisterCallbackOnce Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect. The event handler is automatically unregistered after it has been invoked exactly once.
UnregisterCallback Remove callback from the instance.
Blur Tell the element to release the focus.
Focus Attempt to give the focus to this element.
Add Add an element to this element's contentContainer
AddToClassList Adds a class to the class list of the element in order to assign styles from USS. Note the class name is case-sensitive.
BringToFront Brings this element to the end of its parent children list. The element will be visually in front of any overlapping sibling elements.
Children Returns the elements from its contentContainer.
ClassListContains Searches for a class in the class list of this element.
Clear Remove all child elements from this element's contentContainer
ClearBinding Removes a binding from the element.
ClearBindings Removes all bindings from the element.
ClearClassList Removes all classes from the class list of this element. AddToClassList
Contains Checks if this element is an ancestor of the specified child element.
ContainsPoint Checks if the specified point intersects with this VisualElement's layout.
ElementAt Retrieves the child element at a specific index.
EnableInClassList Enables or disables the class with the given name.
FindAncestorUserData Searches up the hierarchy of this VisualElement and retrieves stored userData, if any is found.
FindCommonAncestor Finds the lowest common ancestor between two VisualElements inside the VisualTree hierarchy.
GetBinding Gets the binding instance for the provided targeted property.
GetBindingInfos Gets information on all the bindings of the current element.
GetClasses Retrieve the classes for this element.
GetDataSourceContext Queries the dataSource and dataSourcePath of a binding object.
GetFirstAncestorOfType Walks up the hierarchy, starting from this element's parent, and returns the first VisualElement of this type
GetFirstOfType Walks up the hierarchy, starting from this element, and returns the first VisualElement of this type
GetHierarchicalDataSourceContext Queries the dataSource and dataSourcePath inherited from the hierarchy.
HasBinding Allows to know if a target property has a binding associated to it.
IndexOf Retrieves the child index of the specified VisualElement.
Insert Insert an element into this element's contentContainer
MarkDirtyRepaint Triggers a repaint of the VisualElement on the next frame. This method is called internally when a change occurs that requires a repaint, such as when UIElements.BaseField_1.value is changed or the text in a Label. If you are implementing a custom control, you can call this method to trigger a repaint when a change occurs that requires a repaint such as when using generateVisualContent to render a mesh and the mesh data has now changed.
PlaceBehind Places this element right before the sibling element in their parent children list. If the element and the sibling position overlap, the element will be visually behind of its sibling.
PlaceInFront Places this element right after the sibling element in their parent children list. If the element and the sibling position overlap, the element will be visually in front of its sibling.
Remove Removes this child from the contentContainerhierarchy.
RemoveAt Remove the child element located at this position from this element's contentContainer
RemoveFromClassList Removes a class from the class list of the element.
RemoveFromHierarchy Removes this element from its parent hierarchy.
SendEvent Sends an event to the event handler.
SendToBack Sends this element to the beginning of its parent children list. The element will be visually behind any overlapping sibling elements.
SetBinding Assigns a binding between a target and a source.
SetEnabled Changes the VisualElement enabled state. A disabled VisualElement does not receive most events.
Sort Reorders child elements from this VisualElement contentContainer.
ToggleInClassList Toggles between adding and removing the given class name from the class list.
TryGetBinding Gets the binding instance for the provided targeted property.
TryGetDataSourceContext Queries the dataSource and dataSourcePath of a binding object.

Protected Methods

CreateViewController Creates the view controller for this view. Override this method in inheritors to change the controller type.
HandleEventBubbleUp Executes logic on this element during the BubbleUp phase, immediately before this element's BubbleUp callbacks. Calling StopPropagation will prevent further invocations of this method along the propagation path.
HandleEventTrickleDown Executes logic on this element during the TrickleDown phase, immediately after this element's TrickleDown callbacks. Calling StopPropagation will prevent further invocations of this method along the propagation path.
NotifyPropertyChanged Informs the data binding system that a property of a control has changed.

Events

canStartDrag Called when a drag operation wants to start in this collection view.
dragAndDropUpdate Called when a drag operation updates in this collection view.
handleDrop Called when a drag operation is released in this collection view.
itemIndexChanged Called when an item is moved in the itemsSource.
itemsChosen Callback triggered when the user acts on a selection of one or more items, for example by double-clicking or pressing Enter.
itemsSourceChanged Called when the itemsSource is reassigned or changes size.
onItemsChosen Obsolete. Use BaseVerticalCollectionView.itemsChosen instead.
onSelectedIndicesChange Obsolete. Use BaseVerticalCollectionView.selectedIndicesChanged instead.
onSelectionChange Obsolete. Use BaseVerticalCollectionView.selectionChanged instead.
selectedIndicesChanged Callback triggered when the selection changes.
selectionChanged Callback triggered when the selection changes.
setupDragAndDrop Called when a drag operation starts in this collection view.