UDreamExpandableArea

本页由 DreamGUIReferenceDocs commandlet 从反射生成，正文是头文件注释的原文（英文），所以不翻译——这样它永远和代码一致。概念讲解见核心概念。

Declared in Public/Controls/DreamExpandableArea.h.

A header that toggles, and the content it hides.

Three nodes and one behaviour: a column, a clickable header face with an indicator and a label on it, and a content column below. The header is a UUIButton on its own face, exactly as DreamButton builds one -- an expander IS a button whose click means "show the rest" -- so hover, press and navigation come from the library's one selectable rather than from a second interaction story.

HOW A CONSUMER PUTS CONTENT IN IT, and which idiom that is, because there are two in this codebase and only one is reachable from here:

Native.ExpandableArea Details {
    Label = "Advanced"
    Text Body { Text = "..." }

Properties

Name	Type	Category	In the details panel	From Blueprint	Description
`Style`	`FDreamExpandableAreaStyle`	Expandable Area	yes	`GetStyle` / `SetStyle`	This instance's own look. The project sheet wins while StyleSource says so AND a sheet actually exists; with no sheet in the project this IS the look in effect -- which is why it stays editable instead of being gated on the enum: the old edit condition greyed the exact values that were driving the control.
`Label`	`FText`	Expandable Area	yes	`GetLabel` / `SetLabel`	The words on the header.
`bIsExpanded`	`bool`	Expandable Area	yes	`GetIsExpanded` / `SetIsExpanded`	Whether the content shows. A property so .dui, the designer and bindings can see it and so an author can ship a section already open; every road that CHANGES it goes through SetIsExpanded, which is the only thing that broadcasts.
`MaxHeight`	`float`	Expandable Area	yes	`GetMaxHeight` / `SetMaxHeight`	A ceiling on the CONTENT's share of the control's height, in local units -- UMG's MaxHeight.
`ExpansionDuration`	`float`	Expandable Area	yes	`GetExpansionDuration` / `SetExpansionDuration`	How long the open and close take, in seconds. Zero (the default) is instant.
`RootNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only
`HeaderNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	The clickable face, and the node whose height IS the style's HeaderHeight. Bound from the part named "HeaderFace" -- the FIELD keeps its name, the part does not; see the class comment for why the two differ.
`HeaderRowNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	The indicator-and-label row inside the header. See the tree comment for why it is its own node.
`ArrowNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	The built-in glyph indicator. Asleep whenever the state's brush carries an image instead.
`ArrowMarkNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	The image indicator, the glyph's stand-in. Exactly one of the two is awake.
`LabelNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only
`ContentNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	Where a consumer's content lives, and the node that is switched off when collapsed.
`HeaderBehaviour`	`TObjectPtr<UUIButton>`	Expandable Area	-	read only
`HeaderSlotNode`	`TObjectPtr<UDreamWidget>`	Expandable Area	-	read only	The header's hole, in the stock label's place. Empty is the normal state.

Functions

Function	Kind	Description
`UDreamWidget* GetContent()`	pure	The first widget in the content column, or null while it is empty.
`float GetExpansionDuration()`	pure	Get Expansion Duration
`bool GetIsExpanded()`	pure	Get Is Expanded
`FText GetLabel()`	pure	Get Label
`float GetMaxHeight()`	pure	Get Max Height
`FDreamExpandableAreaStyle GetStyle()`	pure	Get Style
`void SetContent(UDreamWidget* InContent)`	callable	Put InContent in the content column, taking it from wherever it currently hangs.
`void SetExpansionDuration(float InExpansionDuration)`	callable	How long the NEXT open or close takes. Nothing is re-run: a duration describes a move that has not happened yet, and replaying the current one to honour a new speed would animate a section the player already finished opening.
`void SetIsExpanded(bool bInIsExpanded)`	callable	Silent when the flag does not move; otherwise pushes the visuals and broadcasts both events.
`void SetLabel(FText InLabel)`	callable	The words on the header, written through to the label the control owns.
`void SetMaxHeight(float InMaxHeight)`	callable	Re-measures at once: the ceiling is part of the height this control claims.
`void SetStyle(FDreamExpandableAreaStyle InStyle)`	callable	This instance's whole look, replaced and pushed. See UDreamButton::SetStyle for the caveat.
`void ToggleExpansion()`	callable	What the header click does, callable without a pointer.

Events

Event	Signature	Description
`OnExpansionChanged`	`void DreamExpandableAreaExpansionChangedEvent__DelegateSignature(bool bIsExpanded)`	Fired whenever the expanded flag moves, from a click or from code.
`OnValueChangedBP`	`void DreamExpandableAreaExpansionChangedEvent__DelegateSignature(bool bIsExpanded)`	The `<->` convention: two-way bindings synthesize their reverse route against this exact name, so a value control carries it alongside its spoken events. Fires with them.

Compared with UMG

Every Blueprint-facing member of the UMG class, and where it went. adopt: same name, same meaning. map: here under another name or on another type. reject: deliberately absent, with the reason.

UMG	Member	Status	Here	Note
`UExpandableArea`	`Style`	adopt	`Style`	FDreamExpandableAreaStyle: the header's height, its five state colours, the label, and the content area's background and padding.
`UExpandableArea`	`BorderBrush`	map	`FDreamExpandableAreaStyle::ContentBackground`	A colour rather than an FSlateBrush: the content area is a procedural rect, and what an expander's frame is in this family is that rect's fill. A picture behind the content is a Native.Border around it.
`UExpandableArea`	`BorderColor`	map	`FDreamExpandableAreaStyle::ContentBackground`	One colour where UMG has a brush and a tint over it, for the reason above: there is no brush here for a second colour to multiply.
`UExpandableArea`	`bIsExpanded`	adopt	`bIsExpanded`	Authored open or closed; every road that CHANGES it goes through SetIsExpanded, which is what broadcasts.
`UExpandableArea`	`MaxHeight`	adopt	`MaxHeight`	Zero is no ceiling, which is what this control has always done.
`UExpandableArea`	`HeaderPadding`	map	`FDreamExpandableAreaStyle::HeaderPadding`	In the style, because how a project's section headers are inset is a theme decision.
`UExpandableArea`	`AreaPadding`	map	`FDreamExpandableAreaStyle::ContentPadding`	Named for what it pads rather than for the widget it sits on.
`UExpandableArea`	`OnExpansionChanged`	adopt	`OnExpansionChanged`	Fires from a click and from code alike.
`UExpandableArea`	`GetIsExpanded`	adopt	`GetIsExpanded`
`UExpandableArea`	`SetIsExpanded`	adopt	`SetIsExpanded`
`UExpandableArea`	`SetIsExpanded_Animated`	map	`ExpansionDuration`	A duration rather than a second function: whether an expander animates is a property of the expander, not of the caller, so every road (a click, a binding, code) gets the same open. Zero is instant, which is what every expander already authored does.
`UExpandableArea`	`SetStyle`	adopt	`SetStyle`	UExpandableArea has no style setter at all (its Style is EditAnywhere only); this is the family's spelling of replacing a look at runtime.

UDreamExpandableArea

Properties

Functions

Events

Compared with UMG

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