Offstage class Null safety

A widget that lays the child out as if it was in the tree, but without painting anything, without making the child available for hit testing, and without taking any room in the parent.

Offstage children are still active: they can receive focus and have keyboard input directed to them.

Animations continue to run in offstage children, and therefore use battery and CPU time, regardless of whether the animations end up being visible.

Offstage can be used to measure the dimensions of a widget without bringing it on screen (yet). To hide a widget from view while it is not needed, prefer removing the widget from the tree entirely rather than keeping it alive in an Offstage subtree.

link
This example shows a FlutterLogo widget when the _offstage member field is false, and hides it without any room in the parent when it is true. When offstage, this app displays a button to get the logo size, which will be displayed in a SnackBar.
To create a local project with this code sample, run:
flutter create --sample=widgets.Offstage.1 mysample

See also:

Inheritance

Constructors

Offstage({Key? key, bool offstage = true, Widget? child})
Creates a widget that visually hides its child.
const

Properties

child → Widget?
The widget below this widget in the tree.
finalinherited
hashCode → int
The hash code for this object.
nonVirtual">@nonVirtualread-onlyinherited
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
offstage → bool
Whether the child is hidden from the rest of the tree.
final
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

createElement() → SingleChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
override
createRenderObject(BuildContext context) → RenderOffstage
Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.
override
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
protected">@protectedinherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
override
didUnmountRenderObject(covariant RenderObject renderObject) → void
A render object previously associated with this widget has been removed from the tree. The given RenderObject will be of the same type as returned by this object's createRenderObject.
protected">@protectedinherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed.
inherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
inherited
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String
A string representation of this object.
inherited
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String
Returns a string representation of this node and its descendants.
inherited
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String
Returns a one-line detailed description of the object.
inherited
toStringShort() → String
A short, textual description of this widget.
inherited
updateRenderObject(BuildContext context, covariant RenderOffstage renderObject) → void
Copies the configuration described by this RenderObjectWidget to the given RenderObject, which will be of the same type as returned by this object's createRenderObject.
override

Operators

operator ==(Object other) → bool
The equality operator.
nonVirtual">@nonVirtualinherited