GetListView class

A scrollable list of widgets arranged linearly.

The GetListView.builder constructor takes an IndexedWidgetBuilder, which builds the children on demand. This constructor is appropriate for list views with a large (or infinite) number of children because the builder is called only for those children that are actually visible.

To control the initial scroll offset of the scroll view, provide a controller with its ScrollController.initialScrollOffset property set.

By default, GetListView will automatically pad the list's scrollable extremities to avoid partial obstructions indicated by MediaQuery's padding. To avoid this behavior, override with a zero padding property.

Construction

While laying out the list, visible children's elements, states and render objects will be created lazily based on existing widgets

Destruction

When a child is scrolled out of view, the associated element subtree, states and render objects are destroyed. A new child at the same position in the list will be lazily recreated along with new elements, states and render objects when it is scrolled back.

Destruction mitigation

In order to preserve state as child elements are scrolled in and out of view, the following options are possible:

• Moving the ownership of non-trivial UI-state-driving business logic out of the list child subtree. For instance, if a list contains posts with their number of upvotes coming from a cached network response, store the list of posts and upvote number in a data model outside the list. Let the list child UI subtree be easily recreate-able from the source-of-truth model object. Use StatefulWidgets in the child widget subtree to store instantaneous UI state only.

• Letting KeepAlive be the root widget of the list child widget subtree that needs to be preserved. The KeepAlive widget marks the child subtree's top render object child for keepalive. When the associated top render object is scrolled out of view, the list keeps the child's render object (and by extension, its associated elements and states) in a cache list instead of destroying them. When scrolled back into view, the render object is repainted as-is (if it wasn't marked dirty in the interim).

  This only works if addAutomaticKeepAlives and addRepaintBoundaries are false since those parameters cause the GetListView to wrap each child widget subtree with other widgets.

• Using AutomaticKeepAlive widgets (inserted by default when addAutomaticKeepAlives is true). AutomaticKeepAlive allows descendant widgets to control whether the subtree is actually kept alive or not. This behavior is in contrast with KeepAlive, which will unconditionally keep the subtree alive.

  As an example, the EditableText widget signals its list child element subtree to stay alive while its text field has input focus. If it doesn't have focus and no other descendants signaled for keepalive via a KeepAliveNotification, the list child element subtree will be destroyed when scrolled away.

  AutomaticKeepAlive descendants typically signal it to be kept alive by using the AutomaticKeepAliveClientMixin, then implementing the AutomaticKeepAliveClientMixin.wantKeepAlive getter and calling AutomaticKeepAliveClientMixin.updateKeepAlive.

The key, scrollDirection, reverse, controller, primary, physics, and shrinkWrap properties on GetListView map directly to the identically named properties on CustomScrollView.

The padding property corresponds to having a SliverPadding in the CustomScrollView.slivers property instead of the list itself, and having the SliverList instead be a child of the SliverPadding.

Inheritance

• Object
• DiagnosticableTree
• Widget
• StatelessWidget
• ScrollView
• GetListView

Available Extensions

• ClickableX
• GetDiagnosticable
• GetPopupMenuWidget
• GetWidgetX
• WidgetMarginX
• WidgetPaddingX
• WidgetSliverBoxX

Constructors

GetListView({required GetSliverBuilder sliverBuilder, GetSliverBuilder? topSliverBuilder, GetSliverBuilder? bottomSliverBuilder, WidgetBuilder? replacementBuilder, bool replace = false, Axis scrollDirection = Axis.vertical, bool reverse = false, ScrollController? controller, bool? primary, ScrollPhysics? physics = const AlwaysBouncingScrollPhysics(), bool shrinkWrap = false, double? cacheExtent, DragStartBehavior dragStartBehavior = DragStartBehavior.start, ScrollViewKeyboardDismissBehavior keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual, String? restorationId, Clip clipBehavior = Clip.hardEdge, Key? key})

const

GetListView.builder({GetSliverBuilder? topSliverBuilder, GetSliverBuilder? bottomSliverBuilder, WidgetBuilder? replacementBuilder, bool replace = false, required GetItemBuilder itemBuilder, List? items, IndexedWidgetBuilder? dividerBuilder, WidgetBuilder? edgeDividerBuilder, WidgetBuilder? headerBuilder, WidgetBuilder? footerBuilder, GetSectionBuilder? sectionBuilder, GetSection? section, int? itemCount, DividerStyle? divider, DividerStyle edgeDivider = DividerStyle.full, EdgeInsetsGeometry? padding, bool addAutomaticKeepAlives = true, bool addRepaintBoundaries = true, bool addSemanticIndexes = true, Axis scrollDirection = Axis.vertical, bool reverse = false, ScrollController? controller, bool? primary, ScrollPhysics? physics = const AlwaysBouncingScrollPhysics(), bool shrinkWrap = false, double? cacheExtent, DragStartBehavior dragStartBehavior = DragStartBehavior.start, ScrollViewKeyboardDismissBehavior keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual, String? restorationId, Clip clipBehavior = Clip.hardEdge, Key? key})

Properties

anchor → double

The relative position of the zero scroll offset.

final, inherited

bottomSliverBuilder → GetSliverBuilder?

final

cacheExtent → double?

The viewport has an area before and after the visible area to cache items that are about to become visible when the user scrolls.

final, inherited

center → Key?

The first child in the GrowthDirection.forward growth direction.

final, inherited

clipBehavior → Clip

The content will be clipped (or not) according to this option.

final, inherited

controller → ScrollController?

An object that can be used to control the position to which this scroll view is scrolled.

final, inherited

dragStartBehavior → DragStartBehavior

Determines the way that drag start behavior is handled.

final, inherited

hashCode → int

The hash code for this object.

no setter, inherited

key → Key?

Controls how one widget replaces another widget in the tree.

final, inherited

keyboardDismissBehavior → ScrollViewKeyboardDismissBehavior

ScrollViewKeyboardDismissBehavior the defines how this ScrollView will dismiss the keyboard automatically.

final, inherited

physics → ScrollPhysics?

How the scroll view should respond to user input.

final, inherited

primary → bool?

Whether this is the primary scroll view associated with the parent PrimaryScrollController.

final, inherited

replace → bool

final

replacementBuilder → WidgetBuilder?

final

restorationId → String?

Restoration ID to save and restore the scroll offset of the scrollable.

final, inherited

reverse → bool

Whether the scroll view scrolls in the reading direction.

final, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

scrollBehavior → ScrollBehavior?

A ScrollBehavior that will be applied to this widget individually.

final, inherited

scrollDirection → Axis

The Axis along which the scroll view's offset increases.

final, inherited

semanticChildCount → int?

The number of children that will contribute semantic information.

final, inherited

shrinkWrap → bool

Whether the extent of the scroll view in the scrollDirection should be determined by the contents being viewed.

final, inherited

sliverBuilder → GetSliverBuilder

final

topSliverBuilder → GetSliverBuilder?

final

Methods

build(BuildContext context) → Widget

Describes the part of the user interface represented by this widget.

inherited

buildSlivers(BuildContext context) → List<Widget>

Build the list of widgets to place inside the viewport.

override

buildViewport(BuildContext context, ViewportOffset offset, AxisDirection axisDirection, List<Widget> slivers) → Widget

Build the viewport.

inherited

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

getDirection(BuildContext context) → AxisDirection

Returns the AxisDirection in which the scroll view scrolls.

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