InheritedNotifier<T extends Listenable> class Null safety

An inherited widget for a Listenable notifier, which updates its dependencies when the notifier is triggered.

This is a variant of InheritedWidget, specialized for subclasses of Listenable, such as ChangeNotifier or ValueNotifier.

Dependents are notified whenever the notifier sends notifications, or whenever the identity of the notifier changes.

Multiple notifications are coalesced, so that dependents only rebuild once even if the notifier fires multiple times between two frames.

Typically this class is subclassed with a class that provides an of static method that calls BuildContext.dependOnInheritedWidgetOfExactType with that class.

The updateShouldNotify method may also be overridden, to change the logic in the cases where notifier itself is changed. The updateShouldNotify method is called with the old notifier in the case of the notifier being changed. When it returns true, the dependents are marked as needing to be rebuilt this frame.

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This example shows three spinning squares that use the value of the notifier on an ancestor InheritedNotifier (SpinModel) to give them their rotation. The InheritedNotifier doesn't need to know about the children, and the notifier argument doesn't need to be an animation controller, it can be anything that implements Listenable (like a ChangeNotifier).

The SpinModel class could just as easily listen to another object (say, a separate object that keeps the value of an input or data model value) that is a Listenable, and get the value from that. The descendants also don't need to have an instance of the InheritedNotifier in order to use it, they just need to know that there is one in their ancestry. This can help with decoupling widgets from their models.

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

See also:

Inheritance
Implementers

Constructors

InheritedNotifier({Key? key, T? notifier, required Widget child})
Create an inherited widget that updates its dependents when notifier sends notifications.
const

Properties

child → Widget
The widget below this widget in the tree.
finalinherited
hashCode → int
The hash code for this object.
nonVirtual">@nonVirtualread-onlyinherited
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
notifier → T?
The Listenable object to which to listen.
final
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

createElement() → InheritedElement
Inflates this configuration to a concrete instance.
override
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
protected">@protectedinherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent 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
updateShouldNotify(covariant InheritedNotifier<T> oldWidget) → bool
Whether the framework should notify widgets that inherit from this widget.
override

Operators

operator ==(Object other) → bool
The equality operator.
nonVirtual">@nonVirtualinherited