ValueListenableBuilder<T> class

A widget whose content stays sync'ed with a ValueListenable.

Given a ValueListenable<T> and a builder which builds widgets from concrete values of T, this class will automatically register itself as a listener of the ValueListenable and call the builder with updated values when the value changes.

Performance optimizations

If your builder function contains a subtree that does not depend on the value of the ValueListenable, 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 ValueListenableBuilder 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.

See also:



ValueListenableBuilder({@required ValueListenable<T> valueListenable, @required ValueWidgetBuilder<T> builder, Widget child })
Creates a ValueListenableBuilder. [...]


builder ValueWidgetBuilder<T>
A ValueWidgetBuilder which builds a widget depending on the valueListenable's value. [...]
child Widget
A valueListenable-independent widget which is passed back to the builder. [...]
valueListenable ValueListenable<T>
The ValueListenable whose value you depend on in order to build. [...]
hashCode → int
The hash code for this object. [...]
read-only, inherited
key Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited


createState() State<StatefulWidget>
Creates the mutable state for this widget at a given location in the tree. [...]
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent 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 toStringDeep. [...]
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns 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 ==(dynamic other) → bool
The equality operator. [...]