Scrollbar class

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

• EditableText
• ListWheelScrollView
• PageView
• NestedScrollView
• DropdownButton

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

• Object
• DiagnosticableTree
• Widget
• StatefulWidget
• RawScrollbar
• Scrollbar

Available extensions

• ItemExtension

Constructors

Scrollbar({Key? key, required Widget child, ScrollController? controller, bool? thumbVisibility = true, ScrollbarThemeData? style, Duration fadeDuration = const Duration(milliseconds: 300), Duration timeToFade = const Duration(milliseconds: 600), bool? interactive, ScrollNotificationPredicate notificationPredicate = defaultScrollNotificationPredicate, ScrollbarOrientation? scrollbarOrientation, Duration pressDuration = Duration.zero, double? minOverscrollLength})

Creates a fluent-styled scrollbar that wraps the given child.

const

Properties

child → Widget

The widget below this widget in the tree.

final, inherited

controller → ScrollController?

The ScrollController used to implement Scrollbar dragging.

final, inherited

crossAxisMargin → double

Distance from the scrollbar thumb's side to the nearest cross axis edge in logical pixels.

final, inherited

fadeDuration → Duration

The Duration of the fade animation.

final, inherited

hashCode → int

The hash code for this object.

no setter, inherited

interactive → bool?

Whether the Scrollbar should be interactive and respond to dragging on the thumb, or tapping in the track area.

final, inherited

key → Key?

Controls how one widget replaces another widget in the tree.

final, inherited

mainAxisMargin → double

Distance from the scrollbar thumb's start or end to the nearest edge of the viewport in logical pixels. It affects the amount of available paint area.

final, inherited

minOverscrollLength → double?

The preferred smallest size the scrollbar thumb can shrink to when viewport is overscrolled.

final, inherited

minThumbLength → double

The preferred smallest size the scrollbar thumb can shrink to when the total scrollable extent is large, the current visible viewport is small, and the viewport is not overscrolled.

final, inherited

notificationPredicate → ScrollNotificationPredicate

A check that specifies whether a ScrollNotification should be handled by this widget.

final, inherited

padding → EdgeInsets?

The insets by which the scrollbar thumb and track should be padded.

final, inherited

pressDuration → Duration

The Duration of time that a LongPress will trigger the drag gesture of the scrollbar thumb.

final, inherited

radius → Radius?

The Radius of the scrollbar thumb's rounded rectangle corners.

final, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

scrollbarOrientation → ScrollbarOrientation?

Dictates the orientation of the scrollbar.

final, inherited

shape → OutlinedBorder?

The OutlinedBorder of the scrollbar's thumb.

final, inherited

style → ScrollbarThemeData?

The style applied to the scroll bar. If non-null, it's mescled with FluentThemeData.scrollbarThemeData

final

thickness → double?

The thickness of the scrollbar in the cross axis of the scrollable.

final, inherited

thumbColor → Color?

The color of the scrollbar thumb.

final, inherited

thumbVisibility → bool?

Indicates that the scrollbar thumb should be visible, even when a scroll is not underway.

final, inherited

timeToFade → Duration

The Duration of time until the fade animation begins.

final, inherited

trackBorderColor → Color?

The color of the scrollbar track's border.

final, inherited

trackColor → Color?

The color of the scrollbar track.

final, inherited

trackRadius → Radius?

The Radius of the scrollbar track's rounded rectangle corners.

final, inherited

trackVisibility → bool?

Indicates that the scrollbar track should be visible.

final, inherited

Methods

createElement() → StatefulElement

Creates a StatefulElement to manage this widget's location in the tree.

inherited

createState() → RawScrollbarState<Scrollbar>

Creates the mutable state for this widget at a given location in the tree.

override

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

getProperty<T>([dynamic def]) → T?

Available on Widget, provided by the ItemExtension extension

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, int wrapWidth = 65}) → 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