Do not cache itemBuilder calls in a GridView (#61033)

packages/flutter/lib/src/widgets/sliver.dart

@@ -1052,20 +1052,11 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
       performRebuild();
   }
 
-  // We inflate widgets at two different times:
-  //  1. When we ourselves are told to rebuild (see performRebuild).
-  //  2. When our render object needs a new child (see createChild).
-  // In both cases, we cache the results of calling into our delegate to get the widget,
-  // so that if we do case 2 later, we don't call the builder again.
-  // Any time we do case 1, though, we reset the cache.
-
-  final Map<int, Widget> _childWidgets = HashMap<int, Widget>();
   final SplayTreeMap<int, Element> _childElements = SplayTreeMap<int, Element>();
   RenderBox _currentBeforeChild;
 
   @override
   void performRebuild() {
-    _childWidgets.clear(); // Reset the cache, as described above.
     super.performRebuild();
     _currentBeforeChild = null;
     assert(_currentlyUpdatingChildIndex == null);
@@ -1133,7 +1124,7 @@ class SliverMultiBoxAdaptorElement extends RenderObjectElement implements Render
   }
 
   Widget _build(int index) {
-    return _childWidgets.putIfAbsent(index, () => widget.delegate.build(this, index));
+    return widget.delegate.build(this, index);
   }
 
   @override

packages/flutter/test/widgets/grid_view_test.dart

@@ -566,4 +566,40 @@ void main() {
     expect(tester.getTopLeft(find.byKey(target)), const Offset(606.0, 0.0));
     expect(tester.getBottomRight(find.byKey(target)), const Offset(800.0, 194.0));
   });
+
+  testWidgets('GridView does not cache itemBuilder calls', (WidgetTester tester) async {
+    final Map<int, int> counters = <int, int>{};
+
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: GridView.builder(
+        itemCount: 1000,
+        gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3),
+        itemBuilder: (BuildContext context, int index) {
+          counters[index] ??= 0;
+          counters[index] += 1;
+          return SizedBox(
+            key: ValueKey<int>(index),
+            width: 200,
+            height: 200,
+          );
+        },
+      ),
+    ));
+
+    expect(find.byKey(const ValueKey<int>(4)), findsOneWidget);
+    expect(counters[4], 1);
+
+    await tester.fling(find.byType(GridView), const Offset(0, -300), 5000);
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const ValueKey<int>(4)), findsNothing);
+    expect(counters[4], 1);
+
+    await tester.fling(find.byType(GridView), const Offset(0, 300), 5000);
+    await tester.pumpAndSettle();
+
+    expect(find.byKey(const ValueKey<int>(4)), findsOneWidget);
+    expect(counters[4], 2);
+  });
 }