SliverAnimatedOpacity class

Animated version of SliverOpacity which automatically transitions the sliver child's opacity over a given duration whenever the given opacity changes.

Animating an opacity is relatively expensive because it requires painting the sliver child into an intermediate buffer.

Here's an illustration of what using this widget looks like, using a curve of Curves.fastOutSlowIn.

Creates a CustomScrollView with a SliverFixedExtentList and a FloatingActionButton. Pressing the button animates the lists' opacity.

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

Hit testing

Setting the opacity to zero does not prevent hit testing from being applied to the descendants of the SliverAnimatedOpacity widget. This can be confusing for the user, who may not see anything, and may believe the area of the interface where the SliverAnimatedOpacity 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 SliverAnimatedOpacity widget at all when the opacity animation reaches zero.

To avoid such problems, it is generally a good idea to use a SliverIgnorePointer widget when setting the opacity to zero. This prevents interactions with any children in the subtree when the sliver is animating away.

See also:

  • SliverFadeTransition, an explicitly animated version of this widget, where an Animation is provided by the caller instead of being built in.
  • AnimatedOpacity, for automatically transitioning a box child's opacity over a given duration whenever the given opacity changes.


SliverAnimatedOpacity({Key? key, Widget? sliver, required double opacity, Curve curve = Curves.linear, required Duration duration, VoidCallback? onEnd, bool alwaysIncludeSemantics = false})
Creates a widget that animates its opacity implicitly.


alwaysIncludeSemantics bool
Whether the semantic information of the children is always included.
curve Curve
The curve to apply when animating the parameters of this container.
duration Duration
The duration over which to animate the parameters of this container.
hashCode int
The hash code for this object.
no setterinherited
key Key?
Controls how one widget replaces another widget in the tree.
onEnd VoidCallback?
Called every time an animation completes.
opacity double
The target opacity.
runtimeType Type
A representation of the runtime type of the object.
no setterinherited
sliver Widget?
The sliver below this widget in the tree.


createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
createState() ImplicitlyAnimatedWidgetState<SliverAnimatedOpacity>
Creates the mutable state for this widget at a given location in the tree.
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
toString({DiagnosticLevel minLevel =}) String
A string representation of this object.
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants.
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object.
toStringShort() String
A short, textual description of this widget.


operator ==(Object other) bool
The equality operator.