ExtendedListView.builder constructor
- Key? key,
- Axis scrollDirection = Axis.vertical,
- bool reverse = false,
- ScrollController? controller,
- bool? primary,
- ScrollPhysics? physics,
- bool shrinkWrap = false,
- EdgeInsetsGeometry? padding,
- double? itemExtent,
- required IndexedWidgetBuilder itemBuilder,
- int? itemCount,
- bool addAutomaticKeepAlives = true,
- bool addRepaintBoundaries = true,
- bool addSemanticIndexes = true,
- double? cacheExtent,
- int? semanticChildCount,
- DragStartBehavior dragStartBehavior = DragStartBehavior.start,
- required ExtendedListDelegate extendedListDelegate,
- ScrollViewKeyboardDismissBehavior keyboardDismissBehavior = ScrollViewKeyboardDismissBehavior.manual,
- String? restorationId,
- Clip clipBehavior = Clip.hardEdge,
Creates a scrollable, linear array of widgets that are created 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.
Providing a non-null itemCount
improves the ability of the ExtendedListView to
estimate the maximum scroll extent.
The itemBuilder
callback will be called only with indices greater than
or equal to zero and less than itemCount
.
The itemBuilder
should actually create the widget instances when called.
Avoid using a builder that returns a previously-constructed widget; if the
list view's children are created in advance, or all at once when the
ExtendedListView itself is created, it is more efficient to use new ListView
.
Even more efficient, however, is to create the instances on demand using
this constructor's itemBuilder
callback.
The addAutomaticKeepAlives
argument corresponds to the
SliverChildBuilderDelegate.addAutomaticKeepAlives property. The
addRepaintBoundaries
argument corresponds to the
SliverChildBuilderDelegate.addRepaintBoundaries property. The
addSemanticIndexes
argument corresponds to the
SliverChildBuilderDelegate.addSemanticIndexes property. None may be
null.
ExtendedListView.builder by default does not support child reordering. If you are planning to change child order at a later time, consider using ExtendedListView or ExtendedListView.custom.
Implementation
ExtendedListView.builder({
Key? key,
Axis scrollDirection = Axis.vertical,
bool reverse = false,
ScrollController? controller,
bool? primary,
ScrollPhysics? physics,
bool shrinkWrap = false,
EdgeInsetsGeometry? padding,
this.itemExtent,
required IndexedWidgetBuilder itemBuilder,
int? itemCount,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
double? cacheExtent,
int? semanticChildCount,
DragStartBehavior dragStartBehavior = DragStartBehavior.start,
required this.extendedListDelegate,
ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
ScrollViewKeyboardDismissBehavior.manual,
String? restorationId,
Clip clipBehavior = Clip.hardEdge,
}) : assert(itemCount == null || itemCount >= 0),
assert(semanticChildCount == null || semanticChildCount <= itemCount!),
childrenDelegate = SliverChildBuilderDelegate(
itemBuilder,
childCount: itemCount,
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
),
super(
key: key,
scrollDirection: scrollDirection,
reverse: reverse,
controller: controller,
primary: primary,
physics: physics,
shrinkWrap: shrinkWrap,
padding: padding,
cacheExtent: cacheExtent,
semanticChildCount: semanticChildCount ?? itemCount,
dragStartBehavior: dragStartBehavior,
keyboardDismissBehavior: keyboardDismissBehavior,
restorationId: restorationId,
clipBehavior: clipBehavior,
);