OffstageModifier class
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.
{@tool dartpad}
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.
** See code in examples/api/lib/widgets/basic/offstage.0.dart ** {@end-tool}
See also:
- Visibility, which can hide a child more efficiently (albeit less subtly).
- TickerMode, which can be used to disable animations in a subtree.
- The catalog of layout widgets.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatelessWidget
- SingleChildStatelessModifier
- OffstageModifier
- Available extensions
Constructors
- OffstageModifier({Key? key, Widget? child, Key? modifierKey, bool offstage = true})
-
Creates a widget that visually hides its child.
const
Properties
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- modifierKey → Key?
-
The actual key of the widget, which Modifier wrapped
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.
no setterinherited
Methods
-
build(
BuildContext context) → Widget -
Describes the part of the user interface represented by this widget.
inherited
-
buildWithChild(
BuildContext context, Widget? child) → Widget -
A build method that receives an extra
childparameter.override -
createElement(
) → SingleChildStatelessElement -
Create a SingleChildStatelessElement
inherited
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of DiagnosticsNode objects describing this node's
children.
inherited
-
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
inherited
-
modified(
) → Modifier -
Available on Widget, provided by the ModifierTransformer extension
Transform normal widget to Modifier -
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent 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, int wrapWidth = 65}) → 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
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited