ExtendedScrollController class

Controls a scrollable widget.

Scroll controllers are typically stored as member variables in State objects and are reused in each State.build. A single scroll controller can be used to control multiple scrollable widgets, but some operations, such as reading the scroll offset, require the controller to be used with a single scrollable widget.

A scroll controller creates a ScrollPosition to manage the state specific to an individual Scrollable widget. To use a custom ScrollPosition, subclass ExtendedScrollController and override createScrollPosition.

A ExtendedScrollController is a Listenable. It notifies its listeners whenever any of the attached ScrollPositions notify their listeners (i.e. whenever any of them scroll). It does not notify its listeners when the list of attached ScrollPositions changes.

Typically used with ListView, GridView, CustomScrollView.

See also:

• ListView, GridView, CustomScrollView, which can be controlled by a ExtendedScrollController.
• Scrollable, which is the lower-level widget that creates and associates ScrollPosition objects with ExtendedScrollController objects.
• PageController, which is an analogous object for controlling a PageView.
• ScrollPosition, which manages the scroll offset for an individual scrolling widget.
• ScrollNotification and NotificationListener, which can be used to watch the scroll position without using a ExtendedScrollController.

Inheritance

• Object
• ChangeNotifier
• ExtendedScrollController

Implementers

• ExtendedTrackingScrollController

Constructors

ExtendedScrollController.new({double initialScrollOffset = 0.0, bool keepScrollOffset = true, String? debugLabel})

Creates a controller for a scrollable widget.

Properties

debugLabel → String?

A label that is used in the toString output. Intended to aid with identifying scroll controller instances in debug output.

final

hasClients → bool

Whether any ScrollPosition objects have attached themselves to the ExtendedScrollController using the attach method.

no setter

hashCode → int

The hash code for this object.

no setter, inherited

hasListeners → bool

Whether any listeners are currently registered.

no setter, inherited

initialScrollOffset → double

The initial value to use for offset.

no setter

keepScrollOffset → bool

Each time a scroll completes, save the current scroll offset with PageStorage and restore it if this controller's scrollable is recreated.

final

offset → double

The current scroll offset of the scrollable widget.

no setter

position → ScrollPosition

Returns the attached ScrollPosition, from which the actual scroll offset of the ScrollView can be obtained.

no setter

positions → Iterable<ScrollPosition>

The currently attached positions.

no setter

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

addListener(VoidCallback listener) → void

Register a closure to be called when the object changes.

inherited

animateTo(double offset, {required Duration duration, required Curve curve}) → Future<void>

Animates the position from its current value to the given value.

attach(ScrollPosition position) → void

Register the given position with this controller.

createScrollPosition(ScrollPhysics physics, ScrollContext context, ScrollPosition? oldPosition) → ScrollPosition

Creates a ScrollPosition for use by a Scrollable widget.

debugFillDescription(List<String> description) → void

Add additional information to the given description for use by toString.

detach(ScrollPosition position) → void

Unregister the given position with this controller.

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).

override

jumpTo(double value) → void

Jumps the scroll position from its current value to the given value, without animation, and without checking if the new value is in range.

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.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited