AnimatedBuilder 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, construct the widget and pass it a builder function.

For simple cases without additional state, consider using AnimatedWidget.

Despite the name, AnimatedBuilder is not limited to Animations, any subtype of Listenable (such as ChangeNotifier or ValueNotifier) can be used to trigger rebuilds. Although they have identical implementations, if an Animation is not being listened to, consider using a ListenableBuilder for better readability.

Performance optimizations

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

If a pre-built subtree is passed as the child parameter, the AnimatedBuilder will pass it back to the builder function so that it can be incorporated into the build.

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

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.

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

See also:



AnimatedBuilder({Key? key, required Listenable animation, required TransitionBuilder builder, Widget? child})
Creates an animated builder.


animation Listenable
The Listenable supplied to the constructor (typically an Animation).
no setter
builder TransitionBuilder
Called every time the animation notifies about a change.
no setteroverride
child Widget?
The child widget to pass to the builder.
hashCode int
The hash code for this object.
no setterinherited
key Key?
Controls how one widget replaces another widget in the tree.
listenable Listenable
The Listenable supplied to the constructor (typically an Animation).
no setteroverride
runtimeType Type
A representation of the runtime type of the object.
no setterinherited


build(BuildContext context) Widget
Override this method to build widgets that depend on the state of the listenable (e.g., the current value of the animation).
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
createState() State<AnimatedWidget>
Subclasses typically do not override this method.
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.