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 SliverWithKeepAliveWidgets, such as SliverGrid or SliverList.
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.
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
- keepAlive → bool
-
Whether to keep the child alive. [...]
final
- child → Widget
-
The widget below this widget in the tree. [...]
final, inherited
- hashCode → int
-
The hash code for this object. [...]
read-only, inherited
- key → Key
-
Controls how one widget replaces another widget in the tree. [...]
final, inherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited
Methods
-
applyParentData(
RenderObject renderObject) → void -
Write the data from this widget into the given render object's parent data. [...]
override
-
debugCanApplyOutOfTurn(
) → bool -
Whether the ParentDataElement.applyWidgetOutOfTurn method is allowed
with this widget. [...]
override
-
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node. [...]
override
-
createElement(
) → ParentDataElement< SliverWithKeepAliveWidget> -
Inflates this configuration to a concrete instance. [...]
inherited
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of DiagnosticsNode objects describing this node's
children. [...]
@protected, inherited
-
debugDescribeInvalidAncestorChain(
{String description, String ownershipChain, bool foundValidAncestor, Iterable< Widget> badAncestors }) → String -
Subclasses should override this to describe the requirements for using the
ParentDataWidget subclass. It is called when debugIsValidAncestor()
returned false for an ancestor, or when there are extraneous
ParentDataWidgets in the ancestor chain.
inherited
-
debugIsValidAncestor(
RenderObjectWidget ancestor) → bool -
Subclasses should override this method to return true if the given
ancestor is a RenderObjectWidget that wraps a RenderObject that can handle
the kind of ParentData widget that the ParentDataWidget subclass handles. [...]
inherited
-
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 toStringDeep. [...]
inherited
-
toString(
{DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String -
Returns 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
Operators
-
operator ==(
dynamic other) → bool -
The equality operator. [...]
inherited