default CupertinoSliverNavigationBar's stretch to false (#74669)

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

@@ -541,7 +541,7 @@ class _CupertinoNavigationBarState extends State<CupertinoNavigationBar> {
 /// The [stretch] parameter determines whether the nav bar should stretch to
 /// fill the over-scroll area. The nav bar can still expand and contract as the
 /// user scrolls, but it will also stretch when the user over-scrolls if the
-/// [stretch] value is `true`. Defaults to `true`.
+/// [stretch] value is `true`. Defaults to `false`.
 ///
 /// See also:
 ///
@@ -566,7 +566,7 @@ class CupertinoSliverNavigationBar extends StatefulWidget {
     this.padding,
     this.transitionBetweenRoutes = true,
     this.heroTag = _defaultHeroTag,
-    this.stretch = true,
+    this.stretch = false,
   }) : assert(automaticallyImplyLeading != null),
        assert(automaticallyImplyTitle != null),
        assert(
@@ -658,7 +658,12 @@ class CupertinoSliverNavigationBar extends StatefulWidget {
   ///
   /// The nav bar can still expand and contract as the user scrolls, but it will
   /// also stretch when the user over-scrolls if the [stretch] value is `true`.
-  /// Defaults to `true`.
+  ///
+  /// When set to `true`, the nav bar will prevent subsequent slivers from
+  /// accessing overscrolls. This may be undesirable for using overscroll-based
+  /// widgets like the [CupertinoSliverRefreshControl].
+  ///
+  /// Defaults to `false`.
   final bool stretch;
 
   @override

packages/flutter/test/cupertino/nav_bar_test.dart

@@ -1230,6 +1230,7 @@ void main() {
               const CupertinoSliverNavigationBar(
                 trailing: trailingText,
                 largeTitle: titleText,
+                stretch: true,
               ),
               SliverToBoxAdapter(
                 child: Container(

packages/flutter/test/cupertino/refresh_test.dart

@@ -918,6 +918,47 @@ void main() {
 
       expect(tester.takeException(), isNull);
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
+
+    // Test to make sure the refresh sliver's overscroll isn't eaten by the
+    // nav bar sliver https://github.com/flutter/flutter/issues/74516.
+    testWidgets(
+        'properly displays when the refresh sliver is behind the large title nav bar sliver',
+        (WidgetTester tester) async {
+      await tester.pumpWidget(
+        CupertinoApp(
+          home: CustomScrollView(
+            slivers: <Widget>[
+              const CupertinoSliverNavigationBar(
+                largeTitle: Text('Title'),
+              ),
+              CupertinoSliverRefreshControl(
+                builder: mockHelper.builder,
+              ),
+              buildAListOfStuff(),
+            ],
+          ),
+        ),
+      );
+
+      final double initialFirstCellY = tester.getTopLeft(find.widgetWithText(Container, '0')).dy;
+
+      // Drag down but not enough to trigger the refresh.
+      await tester.drag(find.text('0'), const Offset(0.0, 50.0), touchSlopY: 0);
+      await tester.pump();
+
+      expect(mockHelper.invocations.first, matchesBuilder(
+        refreshState: RefreshIndicatorMode.drag,
+        pulledExtent: 50,
+        refreshTriggerPullDistance: 100,  // default value.
+        refreshIndicatorExtent: 60,  // default value.
+      ));
+      expect(mockHelper.invocations, hasLength(1));
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')).dy,
+        initialFirstCellY + 50
+      );
+    }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
   };
 
   final VoidCallback stateMachineTestGroup = () {