DropdownRoutePage should dispose the created ScrollController. (#133941)

Author: polina-c

packages/flutter/lib/src/material/dropdown.dart

@@ -102,9 +102,11 @@ class _DropdownMenuItemButton<T> extends StatefulWidget {
     required this.constraints,
     required this.itemIndex,
     required this.enableFeedback,
+    required this.scrollController,
   });
 
   final _DropdownRoute<T> route;
+  final ScrollController scrollController;
   final EdgeInsets? padding;
   final Rect buttonRect;
   final BoxConstraints constraints;
@@ -131,7 +133,7 @@ class _DropdownMenuItemButtonState<T> extends State<_DropdownMenuItemButton<T>>
         widget.constraints.maxHeight,
         widget.itemIndex,
       );
-      widget.route.scrollController!.animateTo(
+      widget.scrollController.animateTo(
         menuLimits.scrollOffset,
         curve: Curves.easeInOut,
         duration: const Duration(milliseconds: 100),
@@ -205,6 +207,7 @@ class _DropdownMenu<T> extends StatefulWidget {
     this.dropdownColor,
     required this.enableFeedback,
     this.borderRadius,
+    required this.scrollController,
   });
 
   final _DropdownRoute<T> route;
@@ -214,6 +217,7 @@ class _DropdownMenu<T> extends StatefulWidget {
   final Color? dropdownColor;
   final bool enableFeedback;
   final BorderRadius? borderRadius;
+  final ScrollController scrollController;
 
   @override
   _DropdownMenuState<T> createState() => _DropdownMenuState<T>();
@@ -264,6 +268,7 @@ class _DropdownMenuState<T> extends State<_DropdownMenu<T>> {
           constraints: widget.constraints,
           itemIndex: itemIndex,
           enableFeedback: widget.enableFeedback,
+          scrollController: widget.scrollController,
         ),
       ];
 
@@ -304,7 +309,7 @@ class _DropdownMenuState<T> extends State<_DropdownMenu<T>> {
                   platform: Theme.of(context).platform,
                 ),
                 child: PrimaryScrollController(
-                  controller: widget.route.scrollController!,
+                  controller: widget.scrollController,
                   child: Scrollbar(
                     thumbVisibility: true,
                     child: ListView(
@@ -447,7 +452,6 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
   final BorderRadius? borderRadius;
 
   final List<double> itemHeights;
-  ScrollController? scrollController;
 
   @override
   Duration get transitionDuration => _kDropdownMenuDuration;
@@ -572,7 +576,7 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
   }
 }
 
-class _DropdownRoutePage<T> extends StatelessWidget {
+class _DropdownRoutePage<T> extends StatefulWidget {
   const _DropdownRoutePage({
     super.key,
     required this.route,
@@ -603,29 +607,41 @@ class _DropdownRoutePage<T> extends StatelessWidget {
   final BorderRadius? borderRadius;
 
   @override
-  Widget build(BuildContext context) {
-    assert(debugCheckHasDirectionality(context));
+  State<_DropdownRoutePage<T>> createState() => _DropdownRoutePageState<T>();
+}
+
+class _DropdownRoutePageState<T> extends State<_DropdownRoutePage<T>> {
+  late ScrollController _scrollSontroller;
+
+  @override
+  void initState(){
+    super.initState();
 
     // Computing the initialScrollOffset now, before the items have been laid
     // out. This only works if the item heights are effectively fixed, i.e. either
     // DropdownButton.itemHeight is specified or DropdownButton.itemHeight is null
     // and all of the items' intrinsic heights are less than kMinInteractiveDimension.
     // Otherwise the initialScrollOffset is just a rough approximation based on
     // treating the items as if their heights were all equal to kMinInteractiveDimension.
-    if (route.scrollController == null) {
-      final _MenuLimits menuLimits = route.getMenuLimits(buttonRect, constraints.maxHeight, selectedIndex);
-      route.scrollController = ScrollController(initialScrollOffset: menuLimits.scrollOffset);
-    }
+    final _MenuLimits menuLimits = widget.route.getMenuLimits(widget.buttonRect, widget.constraints.maxHeight, widget.selectedIndex);
+    _scrollSontroller = ScrollController(initialScrollOffset: menuLimits.scrollOffset);
+  }
+
+
+  @override
+  Widget build(BuildContext context) {
+    assert(debugCheckHasDirectionality(context));
 
     final TextDirection? textDirection = Directionality.maybeOf(context);
     final Widget menu = _DropdownMenu<T>(
-      route: route,
-      padding: padding.resolve(textDirection),
-      buttonRect: buttonRect,
-      constraints: constraints,
-      dropdownColor: dropdownColor,
-      enableFeedback: enableFeedback,
-      borderRadius: borderRadius,
+      route: widget.route,
+      padding: widget.padding.resolve(textDirection),
+      buttonRect: widget.buttonRect,
+      constraints: widget.constraints,
+      dropdownColor: widget.dropdownColor,
+      enableFeedback: widget.enableFeedback,
+      borderRadius: widget.borderRadius,
+      scrollController: _scrollSontroller,
     );
 
     return MediaQuery.removePadding(
@@ -638,16 +654,22 @@ class _DropdownRoutePage<T> extends StatelessWidget {
         builder: (BuildContext context) {
           return CustomSingleChildLayout(
             delegate: _DropdownMenuRouteLayout<T>(
-              buttonRect: buttonRect,
-              route: route,
+              buttonRect: widget.buttonRect,
+              route: widget.route,
               textDirection: textDirection,
             ),
-            child: capturedThemes.wrap(menu),
+            child: widget.capturedThemes.wrap(menu),
           );
         },
       ),
     );
   }
+
+  @override
+  void dispose() {
+    _scrollSontroller.dispose();
+    super.dispose();
+  }
 }
 
 // This widget enables _DropdownRoute to look up the sizes of

packages/flutter/test/material/paginated_data_table_test.dart

@@ -6,6 +6,7 @@ import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import 'data_table_test_utils.dart';
 
@@ -66,7 +67,7 @@ class TestDataSource extends DataTableSource {
 void main() {
   final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();
 
-  testWidgets('PaginatedDataTable paging', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('PaginatedDataTable paging', (WidgetTester tester) async {
     final TestDataSource source = TestDataSource();
     addTearDown(source.dispose);