SnapshotWidget class
A widget that can replace its child with a snapshotted version of the child.
A snapshot is a frozen texture-backed representation of all child pictures and layers stored as a ui.Image.
This widget is useful for performing short animations that would otherwise be expensive or that cannot rely on raster caching. For example, scale and skew animations are often expensive to perform on complex children, as are blurs. For a short animation, a widget that contains these expensive effects can be replaced with a snapshot of itself and manipulated instead.
For example, the Android Q ZoomPageTransitionsBuilder uses a snapshot widget for the forward and entering route to avoid the expensive scale animation. This also has the effect of briefly pausing any animations on the page.
Generally, this widget should not be used in places where users expect the child widget to continue animating or to be responsive, such as an unbounded animation.
Caveats:
-
The contents of platform views cannot be captured by a snapshot widget. If a platform view is encountered, then the snapshot widget will determine how to render its children based on the SnapshotMode. This defaults to SnapshotMode.normal which will throw an exception if a platform view is encountered.
-
The snapshotting functionality of this widget is not supported on the HTML backend of Flutter for the Web. Setting SnapshotController.allowSnapshotting to true may cause an error to be thrown. On the CanvasKit backend of Flutter, the performance of using this widget may regress performance due to the fact that both the UI and engine share a single thread.
- Inheritance
Constructors
- SnapshotWidget({Key? key, SnapshotMode mode = SnapshotMode.normal, SnapshotPainter painter = const _DefaultSnapshotPainter(), bool autoresize = false, required SnapshotController controller, required Widget? child})
-
Create a new SnapshotWidget.
const
Properties
- autoresize → bool
-
Whether or not changes in render object size should automatically re-create
the snapshot.
final
- child → Widget?
-
The widget below this widget in the tree.
finalinherited
- controller → SnapshotController
-
The controller that determines when to display the children as a snapshot.
final
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- mode → SnapshotMode
-
Configuration that controls how the snapshot widget decides to paint its children.
final
- painter → SnapshotPainter
-
The painter used to paint the child snapshot or child widgets.
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) → RenderObject -
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.
inherited
-
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 RenderObject 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