AnimatedBuilderModifier class

A general-purpose widget for building animations.

AnimatedBuilder is useful for more complex widgets that wish to include an animation as part of a larger build function. To use AnimatedBuilder, simply construct the widget and pass it a builder function.

For simple cases without additional state, consider using AnimatedWidget.

Performance optimizations

If your builder function contains a subtree that does not depend on the animation, it's more efficient to build that subtree once instead of rebuilding it on every animation tick.

If you pass the pre-built subtree as the child parameter, the AnimatedBuilder will pass it back to your builder function so that you can incorporate it into your build.

Using this pre-built child is entirely optional, but can improve performance significantly in some cases and is therefore a good practice.

{@tool dartpad} This code defines a widget that spins a green square continually. It is built with an AnimatedBuilder and makes use of the child feature to avoid having to rebuild the Container each time.

** See code in examples/api/lib/widgets/transitions/animated_builder.0.dart ** {@end-tool}

Improve rebuilds performance using AnimatedBuilder

Despite the name, AnimatedBuilder is not limited to Animations. Any subtype of Listenable (such as ChangeNotifier and ValueNotifier) can be used with an AnimatedBuilder to rebuild only certain parts of a widget when the Listenable notifies its listeners. This technique is a performance improvement that allows rebuilding only specific widgets leaving others untouched.

{@tool dartpad} The following example implements a simple counter that utilizes an AnimatedBuilder to limit rebuilds to only the Text widget. The current count is stored in a ValueNotifier, which rebuilds the AnimatedBuilder's contents when its value is changed.

** See code in examples/api/lib/foundation/change_notifier/change_notifier.0.dart ** {@end-tool}

Constructors

AnimatedBuilderModifier({Key? key, Widget? child, Key? modifierKey, required Listenable animation, required TransitionBuilder builder}): Creates an animated builder.
const

Properties

animation → Listenable: Animation listenable
final
builder → TransitionBuilder: Called every time the animation changes value.
final
hashCode → int: The hash code for this object.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
modifierKey → Key?: The actual key of the widget, which Modifier wrapped
finalinherited
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

build(BuildContext context) → Widget: Describes the part of the user interface represented by this widget.
inherited
buildWithChild(BuildContext context, Widget? child) → Widget: A build method that receives an extra child parameter.
override
createElement() → SingleChildStatelessElement: Create a SingleChildStatelessElement
inherited
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
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

Operators

operator ==(Object other) → bool: The equality operator.
inherited