[CupertinoActionSheet] Support legacy buttons (flutter#151136)

Fixes flutter#150980

This PR allows buttons implemented with `GestureDetector.onTap` to be selected in the action sheet.

Author: dkwingsmt

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

@@ -546,21 +546,35 @@ class _SlidingTapGestureRecognizer extends VerticalDragGestureRecognizer {
       if (event is PointerMoveEvent) {
         onResponsiveUpdate?.call(event.position);
       }
-      // If this gesture has a competing gesture (such as scrolling), and the
-      // pointer has not moved far enough to get this panning accepted, a
-      // pointer up event should still be considered as an accepted tap up.
-      // Manually accept this gesture here, which triggers onDragEnd.
+      // Sliding tap needs to handle 'up' events differently compared to typical
+      // drag gestures. If there's another gesture recognizer (like scrolling)
+      // competing and the pointer hasn't moved beyond the tolerance limit
+      // (slop), this gesture must still be accepted.
+      //
+      // Simply calling `accept()` here to handle this won't work because it
+      // would break backward compatibility with legacy buttons (see
+      // https://github.com/flutter/flutter/issues/150980 for more details).
+      // Legacy buttons recognize taps using `GestureDetector.onTap`, which
+      // neither accepts nor rejects for short taps. Instead, they wait for the
+      // default resolution as the last contender in the gesture arena.
+      //
+      // Therefore, this gesture should also follow the same strategy of not
+      // immediately accepting or rejecting. This allows tap gestures to take
+      // precedence for being inner, while sliding taps can take precedence over
+      // scroll gestures when the latter give up.
       if (event is PointerUpEvent) {
-        resolve(GestureDisposition.accepted);
         stopTrackingPointer(_primaryPointer!);
         onResponsiveEnd?.call(event.position);
-      } else {
-        super.handleEvent(event);
+        _primaryPointer = null;
+        // Do not call `super.handleEvent`, which gives up the pointer and thus
+        // rejects the gesture.
+        return;
       }
-      if (event is PointerUpEvent || event is PointerCancelEvent) {
+      if (event is PointerCancelEvent) {
         _primaryPointer = null;
       }
     }
+    super.handleEvent(event);
   }
 
   @override

packages/flutter/test/cupertino/action_sheet_test.dart

@@ -1155,6 +1155,52 @@ void main() {
     expect(pressed, null);
   });
 
+  testWidgets('Taps on legacy button calls onPressed and renders correctly', (WidgetTester tester) async {
+    // Legacy buttons are implemented with [GestureDetector.onTap]. Apps that
+    // use customized legacy buttons should continue to work.
+    //
+    // Regression test for https://github.com/flutter/flutter/issues/150980 .
+    bool wasPressed = false;
+    await tester.pumpWidget(
+      createAppWithButtonThatLaunchesActionSheet(
+        Builder(builder: (BuildContext context) {
+          return CupertinoActionSheet(
+            actions: <Widget>[
+              LegacyAction(
+                child: const Text('Legacy'),
+                onPressed: () {
+                  expect(wasPressed, false);
+                  wasPressed = true;
+                  Navigator.pop(context);
+                },
+              ),
+              CupertinoActionSheetAction(child: const Text('One'), onPressed: () {}),
+              CupertinoActionSheetAction(child: const Text('Two'), onPressed: () {}),
+            ],
+          );
+        }),
+      ),
+    );
+
+    await tester.tap(find.text('Go'));
+    await tester.pumpAndSettle();
+    expect(wasPressed, isFalse);
+
+    // Push the legacy button and hold for a while to activate the pressing effect.
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.text('Legacy')));
+    await tester.pump(const Duration(seconds: 1));
+    expect(wasPressed, isFalse);
+    await expectLater(
+      find.byType(CupertinoActionSheet),
+      matchesGoldenFile('cupertinoActionSheet.legacyButton.png'),
+    );
+
+    await gesture.up();
+    await tester.pumpAndSettle();
+    expect(wasPressed, isTrue);
+    expect(find.text('Legacy'), findsNothing);
+  });
+
   testWidgets('Action sheet width is correct when given infinite horizontal space', (WidgetTester tester) async {
     await tester.pumpWidget(
       createAppWithButtonThatLaunchesActionSheet(
@@ -2054,3 +2100,32 @@ class OverrideMediaQuery extends StatelessWidget {
     );
   }
 }
+
+// Old-style action sheet buttons, which are implemented with
+// `GestureDetector.onTap`.
+class LegacyAction extends StatelessWidget {
+  const LegacyAction({
+    super.key,
+    required this.onPressed,
+    required this.child,
+  });
+
+  final VoidCallback onPressed;
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: onPressed,
+      behavior: HitTestBehavior.opaque,
+      child: ConstrainedBox(
+        constraints: const BoxConstraints(minHeight: 57),
+        child: Container(
+          alignment: AlignmentDirectional.center,
+          padding: const EdgeInsets.symmetric(vertical: 16.0, horizontal: 10.0),
+          child: child,
+        ),
+      ),
+    );
+  }
+}