Listenable class abstract
An object that maintains a list of listeners.
The listeners are typically used to notify clients that the object has been updated.
There are two variants of this interface:
- ValueListenable, an interface that augments the Listenable interface with the concept of a current value.
Many classes in the framework API use or implement these interfaces. The following subclasses are especially relevant:
-
ChangeNotifier, which can be subclassed or mixed in to create objects that implement the Listenable interface.
-
ValueNotifier, which implements the ValueListenable interface with a mutable value that triggers the notifications when modified.
The terms "notify clients", "send notifications", "trigger notifications", and "fire notifications" are used interchangeably.
See also:
- ValueListenableBuilder, a widget that uses a builder callback to rebuild whenever a ValueListenable object triggers its notifications, providing the builder with the value of the object.
- Listenable.merge, which creates a Listenable that triggers notifications whenever any of a list of other Listenables trigger their notifications.
- Implementers
Constructors
- Listenable()
-
Abstract const constructor. This constructor enables subclasses to provide
const constructors so that they can be used in const expressions.
const
-
Listenable.merge(List<
Listenable?> listenables) -
Return a Listenable that triggers when any of the given Listenables
themselves trigger.
factory
Properties
- hashCode → int
-
The hash code for this object.
no setterinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
addListener(
VoidCallback listener) → void - Register a closure to be called when the object notifies its listeners.
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
removeListener(
VoidCallback listener) → void - Remove a previously registered closure from the list of closures that the object notifies.
-
toString(
) → String -
A string representation of this object.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited