LitScrollbar class

A scrollbar widget providing an interactive scrollbar on it's child widget.

The default Material Scrollbar is slightly customized to provide a consistant styling across all instances.

A scrollbar thumb indicates which portion of a ScrollView is actually visible.

By default, the thumb will fade in and out as the child scroll view scrolls. When thumbVisibility is true, the scrollbar thumb will remain visible without the fade animation. This requires that the ScrollController associated with the Scrollable widget is provided to controller, or that the PrimaryScrollController is being used by that Scrollable widget.

If the scrollbar is wrapped around multiple ScrollViews, it only responds to the nearest ScrollView and shows the corresponding scrollbar thumb by default. The notificationPredicate allows the ability to customize which ScrollNotifications the Scrollbar should listen to.

If the child ScrollView is infinitely long, the RawScrollbar will not be painted. In this case, the scrollbar cannot accurately represent the relative location of the visible area, or calculate the accurate delta to apply when dragging on the thumb or tapping on the track.

Interaction

Scrollbars are interactive and can use the PrimaryScrollController if a controller is not set. Interactive Scrollbar thumbs can be dragged along the main axis of the ScrollView to change the ScrollPosition. Tapping along the track exclusive of the thumb will trigger a ScrollIncrementType.page based on the relative position to the thumb.

When using the PrimaryScrollController, it must not be attached to more than one ScrollPosition. ScrollViews that have not been provided a ScrollController and have a ScrollView.scrollDirection of Axis.vertical will automatically attach their ScrollPosition to the PrimaryScrollController. Provide a unique ScrollController to each Scrollable in this case to prevent having multiple ScrollPositions attached to the PrimaryScrollController.

{@tool dartpad} This sample shows an app with two scrollables in the same route. Since by default, there is one PrimaryScrollController per route, and they both have a scroll direction of Axis.vertical, they would both try to attach to that controller on mobile platforms. The Scrollbar cannot support multiple positions attached to the same controller, so one ListView, and its Scrollbar have been provided a unique ScrollController. Desktop platforms do not automatically attach to the PrimaryScrollController, requiring ScrollView.primary to be true instead in order to use the PrimaryScrollController.

Alternatively, a new PrimaryScrollController could be created above one of the ListViews.

** See code in examples/api/lib/widgets/scrollbar/raw_scrollbar.0.dart ** {@end-tool}

Automatic Scrollbars on Desktop Platforms

Scrollbars are added to most Scrollable widgets by default on TargetPlatformVariant.desktop platforms. This is done through ScrollBehavior.buildScrollbar as part of an app's ScrollConfiguration. Scrollables that do not use the PrimaryScrollController or have a ScrollController provided to them will receive a unique ScrollController for use with the Scrollbar. In this case, only one Scrollable can be using the PrimaryScrollController, unless interactive is false. To prevent Axis.vertical Scrollables from using the PrimaryScrollController, set ScrollView.primary to false. Scrollable widgets that do not have automatically applied Scrollbars include

Default Scrollbars can be disabled for the whole app by setting a ScrollBehavior with scrollbars set to false.

{@tool snippet}

MaterialApp(
  scrollBehavior: const MaterialScrollBehavior()
    .copyWith(scrollbars: false),
  home: Scaffold(
    appBar: AppBar(title: const Text('Home')),
  ),
)

{@end-tool}

{@tool dartpad} This sample shows how to disable the default Scrollbar for a Scrollable widget to avoid duplicate Scrollbars when running on desktop platforms.

** See code in examples/api/lib/widgets/scrollbar/raw_scrollbar.desktop.0.dart ** {@end-tool}

Inheritance

Constructors

LitScrollbar({Key? key, required Widget child, ScrollController? scrollController, double thickness = 8.0, Radius radius = const Radius.circular(4.0)}): Creates a LitScrollbar.
const

Properties

child → Widget: final
hashCode → int: The hash code for this object.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
radius → Radius: final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
scrollController → ScrollController?: final
thickness → double: final

Methods

build(BuildContext context) → Widget: Describes the part of the user interface represented by this widget.
override
createElement() → StatelessElement: Creates a StatelessElement to manage this widget's location in the tree.
inherited
debugDescribeChildren() → List<DiagnosticsNode>: Returns a list of DiagnosticsNode objects describing this node's children.
inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void: Add additional properties associated with the node.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent 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

Operators

operator ==(Object other) → bool: The equality operator.
inherited