Cupertino date picker should dispose scroll controllers it created. (#135355)

packages/flutter/lib/src/cupertino/date_picker.dart

@@ -1990,6 +1990,10 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   late double totalWidth;
   late double pickerColumnWidth;
 
+  FixedExtentScrollController? _hourScrollController;
+  FixedExtentScrollController? _minuteScrollController;
+  FixedExtentScrollController? _secondScrollController;
+
   @override
   void initState() {
     super.initState();
@@ -2019,6 +2023,10 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   void dispose() {
     PaintingBinding.instance.systemFonts.removeListener(_handleSystemFontsChange);
     textPainter.dispose();
+
+    _hourScrollController?.dispose();
+    _minuteScrollController?.dispose();
+    _secondScrollController?.dispose();
     super.dispose();
   }
 
@@ -2164,8 +2172,11 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   }
 
   Widget _buildHourPicker(EdgeInsetsDirectional additionalPadding, Widget selectionOverlay) {
+    _hourScrollController ??= FixedExtentScrollController(
+        initialItem: selectedHour!
+    );
     return CupertinoPicker(
-      scrollController: FixedExtentScrollController(initialItem: selectedHour!),
+      scrollController: _hourScrollController,
       magnification: _kMagnification,
       offAxisFraction: _calculateOffAxisFraction(additionalPadding.start, 0),
       itemExtent: widget.itemExtent,
@@ -2223,10 +2234,11 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   }
 
   Widget _buildMinutePicker(EdgeInsetsDirectional additionalPadding, Widget selectionOverlay) {
-    return CupertinoPicker(
-      scrollController: FixedExtentScrollController(
+    _minuteScrollController ??= FixedExtentScrollController(
       initialItem: selectedMinute ~/ widget.minuteInterval,
-      ),
+    );
+    return CupertinoPicker(
+      scrollController: _minuteScrollController,
       magnification: _kMagnification,
       offAxisFraction: _calculateOffAxisFraction(
           additionalPadding.start,
@@ -2289,10 +2301,11 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   }
 
   Widget _buildSecondPicker(EdgeInsetsDirectional additionalPadding, Widget selectionOverlay) {
-    return CupertinoPicker(
-      scrollController: FixedExtentScrollController(
+    _secondScrollController ??= FixedExtentScrollController(
       initialItem: selectedSecond! ~/ widget.secondInterval,
-      ),
+    );
+    return CupertinoPicker(
+      scrollController: _secondScrollController,
       magnification: _kMagnification,
       offAxisFraction: _calculateOffAxisFraction(
           additionalPadding.start,

packages/flutter/lib/src/cupertino/picker.dart

@@ -218,6 +218,7 @@ class _CupertinoPickerState extends State<CupertinoPicker> {
   void didUpdateWidget(CupertinoPicker oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (widget.scrollController != null && oldWidget.scrollController == null) {
+      _controller?.dispose();
       _controller = null;
     } else if (widget.scrollController == null && oldWidget.scrollController != null) {
       assert(_controller == null);