🐛 Fix scroll behavior by replacing ScrollController with ZoomScrollController and updating scroll listener parameters across day, multi-day, and week views

Author: kavantrivedi

example/lib/widgets/day_view_widget.dart

@@ -22,6 +22,7 @@ class DayViewWidget extends StatelessWidget {
       timeLineBuilder: (date) => _timeLineBuilder(date, isLtr),
       scrollPhysics: const BouncingScrollPhysics(),
       eventArranger: SideEventArranger(),
+      keepScrollOffset: true,
       showQuarterHours: false,
       showMidnightHour: true,
       hourIndicatorSettings: HourIndicatorSettings(

example/lib/widgets/week_view_widget.dart

@@ -24,6 +24,7 @@ class WeekViewWidget extends StatelessWidget {
       showWeekends: true,
       showMidnightHour: true,
       showLiveTimeLineInAllDays: true,
+      keepScrollOffset: true,
       timeSlotColorBuilder: (_, slotStartTime, __, ___) {
         final hour = slotStartTime.hour;
         final isBusinessHours = hour >= 9 && hour < 17;

lib/src/day_view/_internal_day_view_page.dart

@@ -103,8 +103,6 @@ class InternalDayViewPage<T extends Object?> extends StatefulWidget {
   /// Display full day events.
   final FullDayEventBuilder<T> fullDayEventBuilder;
 
-  final ScrollController dayViewScrollController;
-
   /// Flag to display half hours.
   final bool showHalfHours;
 
@@ -120,8 +118,18 @@ class InternalDayViewPage<T extends Object?> extends StatefulWidget {
   /// Settings for half hour indicator lines.
   final HourIndicatorSettings quarterHourIndicatorSettings;
 
-  /// Scroll listener to set every page's last offset
-  final void Function(ScrollController) scrollListener;
+  /// Scroll listener to set every page's last offset.
+  final void Function(
+    int pageIndex,
+    double offset,
+    ZoomScrollController controller,
+  ) scrollListener;
+
+  /// Page index in the parent [PageView].
+  final int pageIndex;
+
+  /// Whether this page is currently visible in parent [PageView].
+  final bool isCurrentPage;
 
   /// Last scroll offset of day view page.
   final double lastScrollOffset;
@@ -176,9 +184,10 @@ class InternalDayViewPage<T extends Object?> extends StatefulWidget {
     required this.minuteSlotSize,
     required this.scrollNotifier,
     required this.fullDayEventBuilder,
-    required this.dayViewScrollController,
     required this.scrollPhysics,
     required this.scrollListener,
+    required this.pageIndex,
+    required this.isCurrentPage,
     required this.dayDetectorBuilder,
     required this.showHalfHours,
     required this.showQuarterHours,
@@ -210,6 +219,17 @@ class _InternalDayViewPageState<T extends Object?>
       initialScrollOffset: widget.lastScrollOffset,
     );
     scrollController.addListener(_scrollControllerListener);
+
+    if (widget.isCurrentPage) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (!mounted) return;
+        widget.scrollListener(
+          widget.pageIndex,
+          scrollController.offset,
+          scrollController,
+        );
+      });
+    }
   }
 
   @override
@@ -225,6 +245,23 @@ class _InternalDayViewPageState<T extends Object?>
           (oldWidget.heightPerMinute > 0 ? oldWidget.heightPerMinute : 1.0);
       scrollController.prepareZoomJump(scaledOffset);
     }
+
+    if (!widget.keepScrollOffset &&
+        widget.isCurrentPage &&
+        !oldWidget.isCurrentPage &&
+        scrollController.hasClients) {
+      scrollController.jumpTo(widget.lastScrollOffset);
+    }
+
+    if (widget.isCurrentPage && !oldWidget.isCurrentPage) {
+      widget.scrollListener(
+        widget.pageIndex,
+        scrollController.hasClients
+            ? scrollController.offset
+            : widget.lastScrollOffset,
+        scrollController,
+      );
+    }
   }
 
   @override
@@ -236,7 +273,11 @@ class _InternalDayViewPageState<T extends Object?>
   }
 
   void _scrollControllerListener() {
-    widget.scrollListener(scrollController);
+    widget.scrollListener(
+      widget.pageIndex,
+      scrollController.offset,
+      scrollController,
+    );
   }
 
   /// Builds the background color layer for time slots in the day view.
@@ -325,9 +366,7 @@ class _InternalDayViewPageState<T extends Object?>
                 scrollbars: widget.keepScrollOffset,
               ),
               child: SingleChildScrollView(
-                controller: widget.keepScrollOffset
-                    ? scrollController
-                    : widget.dayViewScrollController,
+                controller: scrollController,
                 physics: widget.scrollPhysics,
                 child: SizedBox(
                   height: widget.height,

lib/src/day_view/day_view.dart

@@ -486,13 +486,23 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
   /// Provides data for rendering events and tracks event changes.
   EventController<T>? _controller;
 
-  /// Scroll controller for managing vertical scrolling within the day view.
-  /// Controls scroll position for time axis (top-to-bottom).
-  late ZoomScrollController _scrollController;
+  /// Per-page scroll offset cache keyed by page index.
+  final Map<int, double> _pageOffsets = <int, double>{};
+
+  /// Currently visible page scroll controller.
+  ZoomScrollController? _activeScrollController;
 
   /// Public getter for accessing the scroll controller.
   /// Allows external code to control or listen to scroll events.
-  ScrollController get scrollController => _scrollController;
+  ZoomScrollController get scrollController {
+    final controller = _activeScrollController;
+    if (controller == null || !controller.hasClients) {
+      throw StateError(
+        "ScrollController is not attached to any scroll views yet.",
+      );
+    }
+    return controller;
+  }
 
   /// Callback function triggered when the controller changes or events are modified.
   /// Used to rebuild the view when event data changes.
@@ -505,8 +515,7 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
   @override
   void initState() {
     super.initState();
-    _lastScrollOffset = widget.scrollOffset ??
-        widget.startDuration.inMinutes * widget.heightPerMinute;
+    _lastScrollOffset = _defaultPageOffset;
 
     _reloadCallback = _reload;
     _setDateRange();
@@ -516,10 +525,8 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
     _regulateCurrentDate();
 
     _calculateHeights();
-    _scrollController = ZoomScrollController(
-      initialScrollOffset: _lastScrollOffset,
-    );
     _pageController = PageController(initialPage: _currentIndex);
+    _pageOffsets[_currentIndex] = _lastScrollOffset;
     _eventArranger = widget.eventArranger ?? SideEventArranger<T>();
     _assignBuilders();
   }
@@ -562,6 +569,8 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
         widget.maxDay != oldWidget.maxDay) {
       _setDateRange();
       _regulateCurrentDate();
+      _pageOffsets.clear();
+      _pageOffsets[_currentIndex] = _defaultPageOffset;
 
       _pageController.jumpToPage(_currentIndex);
     }
@@ -575,14 +584,19 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
     _assignBuilders();
 
     if (widget.heightPerMinute != oldWidget.heightPerMinute) {
-      final currentOffset = _scrollController.hasClients
-          ? _scrollController.offset
-          : _lastScrollOffset;
+      final activeController = _activeScrollController;
+      final currentOffset =
+          activeController != null && activeController.hasClients
+              ? activeController.offset
+              : _lastScrollOffset;
       final scaledOffset = currentOffset *
           widget.heightPerMinute /
           (oldWidget.heightPerMinute > 0 ? oldWidget.heightPerMinute : 1.0);
       _lastScrollOffset = scaledOffset;
-      _scrollController.prepareZoomJump(scaledOffset);
+      _pageOffsets[_currentIndex] = scaledOffset;
+      if (activeController != null && activeController.hasClients) {
+        activeController.prepareZoomJump(scaledOffset);
+      }
     }
   }
 
@@ -668,9 +682,12 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
                                 _quarterHourIndicatorSettings,
                             emulateVerticalOffsetBy:
                                 widget.emulateVerticalOffsetBy,
-                            lastScrollOffset: _lastScrollOffset,
-                            dayViewScrollController: _scrollController,
+                            lastScrollOffset: widget.keepScrollOffset
+                                ? (_pageOffsets[index] ?? _defaultPageOffset)
+                                : _defaultPageOffset,
                             scrollPhysics: widget.scrollPhysics,
+                            pageIndex: index,
+                            isCurrentPage: index == _currentIndex,
                             scrollListener: _scrollPageListener,
                             keepScrollOffset: widget.keepScrollOffset,
                             timeSlotColorBuilder: _timeSlotColorBuilder,
@@ -951,9 +968,15 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
         _currentIndex = index;
       });
     }
+    _activeScrollController = null;
+    _lastScrollOffset = widget.keepScrollOffset
+        ? (_pageOffsets[index] ?? _defaultPageOffset)
+        : _defaultPageOffset;
+
     if (!widget.keepScrollOffset) {
+      _pageOffsets[index] = _defaultPageOffset;
       _jumpToOffsetAfterPageTransition(
-        _offsetForDuration(widget.startDuration).toDouble(),
+        _defaultPageOffset,
       );
     }
     widget.onPageChange?.call(_currentDate, _currentIndex);
@@ -990,24 +1013,46 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
 
   void _jumpToOffsetAfterPageTransition(double offset) {
     _runAfterPageTransition(() {
-      if (!_scrollController.hasClients) return;
+      _withAttachedScrollController((controller) {
+        final clampedOffset = offset.clamp(
+          controller.position.minScrollExtent,
+          controller.position.maxScrollExtent,
+        );
 
-      final clampedOffset = offset.clamp(
-        _scrollController.position.minScrollExtent,
-        _scrollController.position.maxScrollExtent,
-      );
+        _lastScrollOffset = clampedOffset.toDouble();
+        _pageOffsets[_currentIndex] = _lastScrollOffset;
+        controller.jumpTo(clampedOffset.toDouble());
+      });
+    });
+  }
+
+  void _withAttachedScrollController(
+    void Function(ZoomScrollController controller) action,
+  ) {
+    final controller = _activeScrollController;
+    if (controller != null && controller.hasClients) {
+      action(controller);
+      return;
+    }
 
-      _lastScrollOffset = clampedOffset.toDouble();
-      _scrollController.jumpTo(clampedOffset.toDouble());
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+
+      final updatedController = _activeScrollController;
+      if (updatedController != null && updatedController.hasClients) {
+        action(updatedController);
+      }
     });
   }
 
+  double get _defaultPageOffset =>
+      widget.scrollOffset ?? _offsetForDuration(widget.startDuration);
+
   double _offsetForDuration(Duration startDuration) {
-    final offSetForSingleMinute = _height / 24 / 60;
     final startDurationInMinutes = startDuration.inMinutes;
     final minuteOffset =
         startDurationInMinutes > 3600 ? 3600 : startDurationInMinutes;
-    return offSetForSingleMinute * minuteOffset;
+    return widget.heightPerMinute * minuteOffset;
   }
 
   /// Animate to next page (next day).
@@ -1208,20 +1253,32 @@ class DayViewState<T extends Object?> extends State<DayView<T>> {
     Duration duration = const Duration(milliseconds: 200),
     Curve curve = Curves.linear,
   }) {
-    _scrollController.animateTo(
-      offset,
-      duration: duration,
-      curve: curve,
-    );
+    _withAttachedScrollController((controller) {
+      controller.animateTo(
+        offset,
+        duration: duration,
+        curve: curve,
+      );
+    });
   }
 
   /// Returns the current visible date in day view.
   DateTime get currentDate =>
       DateTime(_currentDate.year, _currentDate.month, _currentDate.day);
 
   /// Listener for every day page ScrollController
-  void _scrollPageListener(ScrollController controller) {
-    _lastScrollOffset = controller.offset;
+  void _scrollPageListener(
+    int pageIndex,
+    double offset,
+    ZoomScrollController controller,
+  ) {
+    _activeScrollController = controller;
+    if (!widget.keepScrollOffset) return;
+
+    _pageOffsets[pageIndex] = offset;
+    if (pageIndex == _currentIndex) {
+      _lastScrollOffset = offset;
+    }
   }
 }