SliverFadeTransition class

Animates the opacity of a sliver widget.

Creates a CustomScrollView with a SliverFixedExtentList that uses a SliverFadeTransition to fade the list in and out.

To create a local project with this code sample, run:
flutter create --sample=widgets.SliverFadeTransition.1 mysample

Here's an illustration of the FadeTransition widget, the RenderBox equivalent widget, with it's opacity animated by a CurvedAnimation set to Curves.fastOutSlowIn:

Hit testing

Setting the opacity to zero does not prevent hit testing from being applied to the descendants of the SliverFadeTransition widget. This can be confusing for the user, who may not see anything, and may believe the area of the interface where the SliverFadeTransition is hiding a widget to be non-interactive.

With certain widgets, such as Flow, that compute their positions only when they are painted, this can actually lead to bugs (from unexpected geometry to exceptions), because those widgets are not painted by the SliverFadeTransition widget at all when the opacity animation reaches zero.

To avoid such problems, it is generally a good idea to combine this widget with a SliverIgnorePointer that one enables when the opacity animation reaches zero. This prevents interactions with any children in the subtree when the sliver is not visible. For performance reasons, when implementing this, care should be taken not to rebuild the relevant widget (e.g. by calling State.setState) except at the transition point.

Constructors

SliverFadeTransition({Key? key, required Animation<double> opacity, bool alwaysIncludeSemantics = false, Widget? sliver}): Creates an opacity transition.
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.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
opacity → Animation<double>: The animation that controls the opacity of the sliver child.
final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

createElement() → SingleChildRenderObjectElement: RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
createRenderObject(BuildContext context) → RenderSliverAnimatedOpacity: 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.
inherited
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.
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}) → 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 RenderSliverAnimatedOpacity 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.
inherited