SliverOpacity class Null safety
A sliver widget that makes its sliver child partially transparent.
This class paints its sliver child into an intermediate buffer and then blends the sliver back into the scene partially transparent.
For values of opacity other than 0.0 and 1.0, this class is relatively expensive because it requires painting the sliver child into an intermediate buffer. For the value 0.0, the sliver child is simply not painted at all. For the value 1.0, the sliver child is painted immediately without an intermediate buffer.
This example shows a SliverList when the
_visible
member field is true,
and hides it when it is false:
bool _visible = true;
List<Widget> listItems = const <Widget>[
Text('Now you see me,'),
Text("Now you don't!"),
];
SliverOpacity(
opacity: _visible ? 1.0 : 0.0,
sliver: SliverList(
delegate: SliverChildListDelegate(listItems),
),
)
This is more efficient than adding and removing the sliver child widget from the tree on demand.
See also:
- Opacity, which can apply a uniform alpha effect to its child using the RenderBox layout protocol.
- AnimatedOpacity, which uses an animation internally to efficiently animate Opacity.
- Inheritance
Constructors
- SliverOpacity({Key? key, required double opacity, bool alwaysIncludeSemantics = false, Widget? sliver})
-
Creates a sliver that makes its sliver child partially transparent.
const
Properties
- alwaysIncludeSemantics → bool
-
Whether the semantic information of the sliver child is always included.
final
- child → Widget?
-
The widget below this widget in the tree.
finalinherited
- hashCode → int
- The hash code for this object.
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- opacity → double
-
The fraction to scale the sliver child's alpha value.
final
- runtimeType → Type
-
A representation of the runtime type of the object.
read-onlyinherited
Methods
-
createElement(
) → SingleChildRenderObjectElement -
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
-
createRenderObject(
BuildContext context) → RenderSliverOpacity -
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 RenderSliverOpacity 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