WidgetStatesController class
Manages a set of WidgetStates and notifies listeners of changes.
Used by widgets that expose their internal state for the sake of extensions that add support for additional states. See TextButton for an example.
The controller's value is its current set of states. Listeners are notified whenever the value changes. The value should only be changed with update; it should not be modified directly.
The controller's value represents the set of states that a widget's visual properties, typically WidgetStateProperty values, are resolved against. It is not the intrinsic state of the widget. The widget is responsible for ensuring that the controller's value tracks its intrinsic state. For example one cannot request the keyboard focus for a widget by adding WidgetState.focused to its controller. When the widget gains the or loses the focus it will update its controller's value and notify listeners of the change.
When calling setState in a WidgetStatesController listener, use the
SchedulerBinding.addPostFrameCallback to delay the call to setState after
the frame has been rendered. It's generally prudent to use the
SchedulerBinding.addPostFrameCallback because some of the widgets that
depend on WidgetStatesController may call update in their build method.
In such cases, listener's that call setState - during the build phase - will cause
an error.
See also:
- MaterialStatesController, the Material specific version of
WidgetStatesController.
- Inheritance
-
- Object
- ChangeNotifier
- ValueNotifier<
Set< WidgetState> > - WidgetStatesController
Constructors
-
WidgetStatesController([Set<
WidgetState> ? value]) - Creates a WidgetStatesController.
Properties
- hashCode → int
-
The hash code for this object.
no setterinherited
- hasListeners → bool
-
Whether any listeners are currently registered.
no setterinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
-
value
↔ Set<
WidgetState> -
The current value stored in this notifier.
getter/setter pairinherited
Methods
-
addListener(
VoidCallback listener) → void -
Register a closure to be called when the object changes.
inherited
-
dispose(
) → void -
Discards any resources used by the object. After this is called, the
object is not in a usable state and should be discarded (calls to
addListener will throw after the object is disposed).
inherited
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
notifyListeners(
) → void -
Call all the registered listeners.
inherited
-
removeListener(
VoidCallback listener) → void -
Remove a previously registered closure from the list of closures that are
notified when the object changes.
inherited
-
toString(
) → String -
A string representation of this object.
inherited
-
update(
WidgetState state, bool add) → void -
Adds
stateto value ifaddis true, and removes it otherwise, and notifies listeners if value has changed.
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited