KeepAlive class
Mark a child as needing to stay alive even when it's in a lazy list that would otherwise remove it.
This widget is for use in a RenderAbstractViewports, such as Viewport or TwoDimensionalViewport.
This widget is rarely used directly. The SliverChildBuilderDelegate and
SliverChildListDelegate delegates, used with SliverList and
SliverGrid, as well as the scroll view counterparts ListView and
GridView, have an addAutomaticKeepAlives feature, which is enabled by
default, and which causes AutomaticKeepAlive widgets to be inserted around
each child, causing KeepAlive widgets to be automatically added and
configured in response to KeepAliveNotifications.
The same addAutomaticKeepAlives feature is supported by the
TwoDimensionalChildBuilderDelegate and TwoDimensionalChildListDelegate.
Therefore, to keep a widget alive, it is more common to use those notifications than to directly deal with KeepAlive widgets.
In practice, the simplest way to deal with these notifications is to mix AutomaticKeepAliveClientMixin into one's State. See the documentation for that mixin class for details.
- Inheritance
Constructors
Properties
- child → Widget
-
The widget below this widget in the tree.
finalinherited
- debugTypicalAncestorWidgetClass → Type
-
Describes the RenderObjectWidget that is typically used to set up the
ParentData that applyParentData will write to.
no setteroverride
- debugTypicalAncestorWidgetDescription → String
-
Describes the RenderObjectWidget that is typically used to set up the
ParentData that applyParentData will write to.
no setteroverride
- hashCode → int
-
The hash code for this object.
no setterinherited
- keepAlive → bool
-
Whether to keep the child alive.
final
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
applyParentData(
RenderObject renderObject) → void -
Write the data from this widget into the given render object's parent data.
override
-
createElement(
) → ParentDataElement< KeepAliveParentDataMixin> -
Inflates this configuration to a concrete instance.
inherited
-
debugCanApplyOutOfTurn(
) → bool -
Whether the ParentDataElement.applyWidgetOutOfTurn method is allowed
with this widget.
override
-
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.
override
-
debugIsValidRenderObject(
RenderObject renderObject) → bool -
Checks if this widget can apply its parent data to the provided
renderObject.inherited -
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