From a51141a36deb5a70933f970ec3a7f9d6146100aa Mon Sep 17 00:00:00 2001
From: Victor Sanni <victorsanniay@gmail.com>
Date: Tue, 19 Aug 2025 15:31:17 -0700
Subject: [PATCH] Update CupertinoSliverNavigationBar.middle (#173868)

Fixes [CupertinoSliverNavigationBar middle widget does not update/react
when its value
changes](https://github.com/flutter/flutter/issues/173855)
---
 .../flutter/lib/src/cupertino/nav_bar.dart    | 14 +++++++-
 .../flutter/test/cupertino/nav_bar_test.dart  | 36 +++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/cupertino/nav_bar.dart b/packages/flutter/lib/src/cupertino/nav_bar.dart
index 30c9477b116..c7b8e5b1512 100644
--- a/packages/flutter/lib/src/cupertino/nav_bar.dart
+++ b/packages/flutter/lib/src/cupertino/nav_bar.dart
@@ -1202,11 +1202,19 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
     _searchAnimation = CurvedAnimation(parent: _animationController, curve: _kNavBarSearchCurve);
   }
 
+  @override
+  void didUpdateWidget(CupertinoSliverNavigationBar oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (widget.middle != oldWidget.middle) {
+      _updateEffectiveMiddle();
+    }
+  }
+
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
     isPortrait = MediaQuery.orientationOf(context) == Orientation.portrait;
-    effectiveMiddle = widget.middle ?? (isPortrait ? null : widget.largeTitle);
+    _updateEffectiveMiddle();
     _computeScaledHeights();
     _setupSearchableAnimation();
     _scrollableState?.position.isScrollingNotifier.removeListener(_handleScrollChange);
@@ -1234,6 +1242,10 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
     return 0.0;
   }
 
+  void _updateEffectiveMiddle() {
+    effectiveMiddle = widget.middle ?? (isPortrait ? null : widget.largeTitle);
+  }
+
   void _computeScaledHeights() {
     final TextScaler textScaler = MediaQuery.textScalerOf(context);
     scaledSearchFieldHeight =
diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index 5ef266c2198..2633dc4c156 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -3131,6 +3131,42 @@ void main() {
       expect(count, 2);
     },
   );
+
+  testWidgets('Sliver nav bar middle can be updated', (WidgetTester tester) async {
+    setWindowToPortrait(tester);
+    String middle = 'First';
+    late StateSetter setState;
+
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: StatefulBuilder(
+          builder: (BuildContext context, StateSetter stateSetter) {
+            setState = stateSetter;
+            return CustomScrollView(
+              slivers: <Widget>[
+                CupertinoSliverNavigationBar(
+                  largeTitle: const Text('Large title'),
+                  middle: Text(middle),
+                ),
+                const SliverFillRemaining(child: SizedBox(height: 1000.0)),
+              ],
+            );
+          },
+        ),
+      ),
+    );
+
+    expect(find.text('First'), findsOneWidget);
+    expect(find.text('Second'), findsNothing);
+
+    setState(() {
+      middle = 'Second';
+    });
+    await tester.pump();
+
+    expect(find.text('First'), findsNothing);
+    expect(find.text('Second'), findsOneWidget);
+  });
 }
 
 class _ExpectStyles extends StatelessWidget {