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added scroll controller #445

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added scroll controller #445

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29 changes: 23 additions & 6 deletions packages/scrollable_positioned_list/lib/src/scrollable_positioned_list.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -178,6 +178,14 @@ class ScrollablePositionedList extends StatefulWidget {
/// Controller to jump or scroll to a particular position in a
/// [ScrollablePositionedList].
class ItemScrollController {
/// Exposes [ScrollablePositionedList]'s Primary scroll controller
ScrollController? scrollController;

ItemScrollController({ScrollController? scrollController}) {
this.scrollController =
scrollController ?? ScrollController(keepScrollOffset: false);
}

/// Whether any ScrollablePositionedList objects are attached this object.
///
/// If `false`, then [jumpTo] and [scrollTo] must not be called.
Expand Down Expand Up @@ -258,11 +266,11 @@ class ItemScrollController {
class _ScrollablePositionedListState extends State<ScrollablePositionedList>
with TickerProviderStateMixin {
/// Details for the primary (active) [ListView].
var primary = _ListDisplayDetails(const ValueKey('Ping'));
late _ListDisplayDetails primary;

/// Details for the secondary (transitional) [ListView] that is temporarily
/// shown when scrolling a long distance.
var secondary = _ListDisplayDetails(const ValueKey('Pong'));
late _ListDisplayDetails secondary;

final opacity = ProxyAnimation(const AlwaysStoppedAnimation<double>(0));

Expand All @@ -275,7 +283,16 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
@override
void initState() {
super.initState();
ItemPosition? initialPosition = PageStorage.of(context)!.readState(context);
ItemPosition? initialPosition = PageStorage.of(context).readState(context);
primary = _ListDisplayDetails(
widget.itemScrollController?.scrollController ??
ScrollController(keepScrollOffset: false),
const ValueKey('Ping'),
);
secondary = _ListDisplayDetails(
ScrollController(keepScrollOffset: false),
const ValueKey('Pong'),
);
primary.target = initialPosition?.index ?? widget.initialScrollIndex;
primary.alignment =
initialPosition?.itemLeadingEdge ?? widget.initialAlignment;
Expand Down Expand Up @@ -568,7 +585,7 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
.where((ItemPosition position) =>
position.itemLeadingEdge < 1 && position.itemTrailingEdge > 0);
if (itemPositions.isNotEmpty) {
PageStorage.of(context)!.writeState(
PageStorage.of(context).writeState(
context,
itemPositions.reduce((value, element) =>
value.itemLeadingEdge < element.itemLeadingEdge
Expand All @@ -580,10 +597,10 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
}

class _ListDisplayDetails {
_ListDisplayDetails(this.key);
_ListDisplayDetails(this.scrollController, this.key);

final itemPositionsNotifier = ItemPositionsNotifier();
final scrollController = ScrollController(keepScrollOffset: false);
final ScrollController scrollController;

/// The index of the item to scroll to.
int target = 0;
Expand Down