From 1cff1b29b122ce22f675dec563ae74df42b21959 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Klemen=20Tu=C5=A1ar?= <techouse@gmail.com>
Date: Sun, 8 Jun 2025 09:15:28 +0100
Subject: [PATCH 1/5] Fix infinite loop in CupertinoSliverNavigationBar
 collapse animation by adding bounds check for target scroll position

---
 packages/flutter/lib/src/cupertino/nav_bar.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/cupertino/nav_bar.dart b/packages/flutter/lib/src/cupertino/nav_bar.dart
index 681273dda1104..2e0a992e7c13d 100644
--- a/packages/flutter/lib/src/cupertino/nav_bar.dart
+++ b/packages/flutter/lib/src/cupertino/nav_bar.dart
@@ -1297,7 +1297,7 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
               : bottomScrollOffset;
     }
 
-    if (target != null) {
+    if (target != null && target <= position.maxScrollExtent) {
       position.animateTo(
         target,
         // Eyeballed on an iPhone 16 simulator running iOS 18.

From 5860d6d82f34abb474f620eb1ff77d3057166156 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Klemen=20Tu=C5=A1ar?= <techouse@gmail.com>
Date: Sun, 8 Jun 2025 09:27:02 +0100
Subject: [PATCH 2/5] Add bounds check for target scroll position in
 CupertinoSliverNavigationBar collapse animation

---
 packages/flutter/lib/src/cupertino/nav_bar.dart | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/flutter/lib/src/cupertino/nav_bar.dart b/packages/flutter/lib/src/cupertino/nav_bar.dart
index 2e0a992e7c13d..337754015c9cf 100644
--- a/packages/flutter/lib/src/cupertino/nav_bar.dart
+++ b/packages/flutter/lib/src/cupertino/nav_bar.dart
@@ -1297,6 +1297,7 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
               : bottomScrollOffset;
     }
 
+    // If the target is not null and within the scrollable range, animate to it.
     if (target != null && target <= position.maxScrollExtent) {
       position.animateTo(
         target,

From c2528e15505d5ad663fb5c167784ae1bf7e10ce2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Klemen=20Tu=C5=A1ar?= <techouse@gmail.com>
Date: Sun, 8 Jun 2025 12:16:51 +0100
Subject: [PATCH 3/5] Add test to prevent infinite animation loop in
 CupertinoSliverNavigationBar

---
 .../flutter/test/cupertino/nav_bar_test.dart  | 71 +++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index 2175d8edb2a4e..4cda9d3e1cf54 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -3069,6 +3069,77 @@ void main() {
     expect(find.text(largeTitle), findsOneWidget);
     expect(find.byType(CupertinoSearchTextField), findsOneWidget);
   });
+
+  testWidgets(
+    'CupertinoSliverNavigationBar does not enter infinite animation loop when target exceeds maxScrollExtent and prevents buttons from being tapped',
+    (WidgetTester tester) async {
+      setWindowToPortrait(tester);
+
+      const double largeTitleHeight = 52.0;
+
+      final ScrollController scrollController = ScrollController();
+      addTearDown(scrollController.dispose);
+
+      tester.view.devicePixelRatio = 1;
+      tester.binding.platformDispatcher.textScaleFactorTestValue = 1;
+      setWindowToPortrait(tester, size: const Size(402, 874));
+
+      int count = 0;
+
+      await tester.pumpWidget(
+        CupertinoApp(
+          home: CustomScrollView(
+            controller: scrollController,
+            slivers: <Widget>[
+              const CupertinoSliverNavigationBar(largeTitle: Text('Large Title')),
+              SliverToBoxAdapter(
+                child: SizedBox(
+                  // This height will trigger the issue if the target exceeds maxScrollExtent.
+                  height: 805,
+                  child: Center(
+                    child: CupertinoButton(
+                      child: const Text('Press me!'),
+                      onPressed: () {
+                        count++;
+                      },
+                    ),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
+
+      await tester.pumpAndSettle();
+
+      // Verify the button is present
+      expect(find.widgetWithText(CupertinoButton, 'Press me!'), findsOneWidget);
+
+      // Tap the button
+      await tester.tap(find.widgetWithText(CupertinoButton, 'Press me!'));
+      await tester.pump(); // Process the tap
+
+      // Check if the counter has increased
+      expect(count, 1);
+
+      // Scroll a little over the halfway point.
+      final TestGesture scrollGesture = await tester.startGesture(
+        tester.getCenter(find.byType(Scrollable)),
+      );
+      await scrollGesture.moveBy(const Offset(0.0, -(largeTitleHeight / 2) - 1));
+      await scrollGesture.up();
+      // This should not time out or throw an error.
+      await tester.pumpAndSettle();
+
+      // Tap the button
+      await tester.tap(find.widgetWithText(CupertinoButton, 'Press me!'));
+      await tester.pump(); // Process the tap
+
+      // Check if the counter has increased
+      expect(count, 2);
+    },
+  );
 }
 
 class _ExpectStyles extends StatelessWidget {

From 9c1faa4999b40354751bd6350efeefe3db014e76 Mon Sep 17 00:00:00 2001
From: Klemen Tusar <techouse@gmail.com>
Date: Mon, 9 Jun 2025 19:59:46 +0100
Subject: [PATCH 4/5] Update packages/flutter/test/cupertino/nav_bar_test.dart

Co-authored-by: Victor Sanni <victorsanniay@gmail.com>
---
 packages/flutter/test/cupertino/nav_bar_test.dart | 2 --
 1 file changed, 2 deletions(-)

diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index 4cda9d3e1cf54..bf9ea6e78937e 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -3073,8 +3073,6 @@ void main() {
   testWidgets(
     'CupertinoSliverNavigationBar does not enter infinite animation loop when target exceeds maxScrollExtent and prevents buttons from being tapped',
     (WidgetTester tester) async {
-      setWindowToPortrait(tester);
-
       const double largeTitleHeight = 52.0;
 
       final ScrollController scrollController = ScrollController();

From bd375807fdca3dca26a9abfce2b5c223ecfc7a32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Klemen=20Tu=C5=A1ar?= <techouse@gmail.com>
Date: Wed, 11 Jun 2025 20:21:41 +0100
Subject: [PATCH 5/5] Refactor nav bar test for clarity and concise counter
 increment logic.

---
 .../flutter/test/cupertino/nav_bar_test.dart  | 21 +++++++++----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index bf9ea6e78937e..c22673f85eacf 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -3097,9 +3097,7 @@ void main() {
                   child: Center(
                     child: CupertinoButton(
                       child: const Text('Press me!'),
-                      onPressed: () {
-                        count++;
-                      },
+                      onPressed: () => count++,
                     ),
                   ),
                 ),
@@ -3111,14 +3109,14 @@ void main() {
 
       await tester.pumpAndSettle();
 
-      // Verify the button is present
+      // Verify the button is present.
       expect(find.widgetWithText(CupertinoButton, 'Press me!'), findsOneWidget);
 
-      // Tap the button
+      // Tap the button.
       await tester.tap(find.widgetWithText(CupertinoButton, 'Press me!'));
-      await tester.pump(); // Process the tap
+      await tester.pump();
 
-      // Check if the counter has increased
+      // Check if the counter has increased.
       expect(count, 1);
 
       // Scroll a little over the halfway point.
@@ -3127,14 +3125,15 @@ void main() {
       );
       await scrollGesture.moveBy(const Offset(0.0, -(largeTitleHeight / 2) - 1));
       await scrollGesture.up();
-      // This should not time out or throw an error.
+
+      // The crux of this test: this should NOT time out or throw an error.
       await tester.pumpAndSettle();
 
-      // Tap the button
+      // Tap the button.
       await tester.tap(find.widgetWithText(CupertinoButton, 'Press me!'));
-      await tester.pump(); // Process the tap
+      await tester.pump();
 
-      // Check if the counter has increased
+      // Check if the counter has increased.
       expect(count, 2);
     },
   );

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