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Attach Scroll listener to secondary list navigated to an item at long… #496

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Attach Scroll listener to secondary list navigated to an item at long… #496

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23 changes: 14 additions & 9 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 @@ -338,15 +338,7 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
widget.scrollOffsetController?._attach(this);
primary.itemPositionsNotifier.itemPositions.addListener(_updatePositions);
secondary.itemPositionsNotifier.itemPositions.addListener(_updatePositions);
primary.scrollController.addListener(() {
final currentOffset = primary.scrollController.offset;
final offsetChange = currentOffset - previousOffset;
previousOffset = currentOffset;
if (!_isTransitioning |
(widget.scrollOffsetNotifier?.recordProgrammaticScrolls ?? false)) {
widget.scrollOffsetNotifier?.changeController.add(offsetChange);
}
});
primary.scrollController.addListener(_scrollListener);
}

@override
Expand All @@ -369,6 +361,7 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
.removeListener(_updatePositions);
secondary.itemPositionsNotifier.itemPositions
.removeListener(_updatePositions);
primary.scrollController.removeListener(_scrollListener);
_animationController?.dispose();
super.dispose();
}
Expand Down Expand Up @@ -612,9 +605,11 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
if (opacity.value >= 0.5) {
// Secondary [ListView] is more visible than the primary; make it the
// new primary.
primary.scrollController.removeListener(_scrollListener);
var temp = primary;
primary = secondary;
secondary = temp;
primary.scrollController.addListener(_scrollListener);
}
_isTransitioning = false;
opacity.parent = const AlwaysStoppedAnimation<double>(0);
Expand Down Expand Up @@ -652,6 +647,16 @@ class _ScrollablePositionedListState extends State<ScrollablePositionedList>
}
widget.itemPositionsNotifier?.itemPositions.value = itemPositions;
}

void _scrollListener() {
final currentOffset = primary.scrollController.offset;
final offsetChange = currentOffset - previousOffset;
previousOffset = currentOffset;
if (!_isTransitioning |
(widget.scrollOffsetNotifier?.recordProgrammaticScrolls ?? false)) {
widget.scrollOffsetNotifier?.changeController.add(offsetChange);
}
}
}

class _ListDisplayDetails {
Expand Down