Make UiKitViews participate in gesture arenas (#24027)

packages/flutter/lib/src/rendering/platform_view.dart

@@ -36,6 +36,20 @@ enum _PlatformViewState {
   ready,
 }
 
+bool _factoryTypesSetEquals<T>(Set<Factory<T>> a, Set<Factory<T>> b) {
+  if (a == b) {
+    return true;
+  }
+  if (a == null ||  b == null) {
+    return false;
+  }
+  return setEquals(_factoriesTypeSet(a), _factoriesTypeSet(b));
+}
+
+Set<Type> _factoriesTypeSet<T>(Set<Factory<T>> factories) {
+  return factories.map<Type>((Factory<T> factory) => factory.type).toSet();
+}
+
 /// A render object for an Android view.
 ///
 /// Requires Android API level 20 or greater.
@@ -48,11 +62,13 @@ enum _PlatformViewState {
 /// provide bounded layout constraints.
 /// {@endtemplate}
 ///
-/// RenderAndroidView participates in Flutter's [GestureArena]s, and dispatches touch events to the
-/// Android view iff it won the arena. Specific gestures that should be dispatched to the Android
-/// view can be specified with factories in [RenderAndroidView.gestureRecognizers]. If
-/// [RenderAndroidView.gestureRecognizers] is empty, the gesture will be dispatched to the Android
-/// view iff it was not claimed by any other gesture recognizer.
+/// {@template flutter.rendering.platformView.gestures}
+/// The render object participates in Flutter's [GestureArena]s, and dispatches touch events to the
+/// platform view iff it won the arena. Specific gestures that should be dispatched to the platform
+/// view can be specified with factories in the `gestureRecognizers` constructor parameter or
+/// by calling `updateGestureRecognizers`. If the set of gesture recognizers is empty, the gesture
+/// will be dispatched to the platform view iff it was not claimed by any other gesture recognizer.
+/// {@endtemplate}
 ///
 /// See also:
 ///  * [AndroidView] which is a widget that is used to show an Android view.
@@ -94,7 +110,8 @@ class RenderAndroidView extends RenderBox {
   // any newly arriving events there's nothing we need to invalidate.
   PlatformViewHitTestBehavior hitTestBehavior;
 
-  /// Which gestures should be forwarded to the Android view.
+  /// {@template flutter.rendering.platformView.updateGestureRecognizers}
+  /// Updates which gestures should be forwarded to the platform view.
   ///
   /// Gesture recognizers created by factories in this set participate in the gesture arena for each
   /// pointer that was put down on the render box. If any of the recognizers on this list wins the
@@ -105,12 +122,16 @@ class RenderAndroidView extends RenderBox {
   ///
   /// Setting a new set of gesture recognizer factories with the same [Factory.type]s as the current
   /// set has no effect, because the factories' constructors would have already been called with the previous set.
+  /// {@endtemplate}
   ///
   /// Any active gesture arena the Android view participates in is rejected when the
   /// set of gesture recognizers is changed.
   void updateGestureRecognizers(Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers) {
     assert(gestureRecognizers != null);
-    assert(_factoriesTypeSet(gestureRecognizers).length == gestureRecognizers.length);
+    assert(
+    _factoriesTypeSet(gestureRecognizers).length == gestureRecognizers.length,
+    'There were multiple gesture recognizer factories for the same type, there must only be a single '
+        'gesture recognizer factory for each gesture recognizer type.',);
     if (_factoryTypesSetEquals(gestureRecognizers, _gestureRecognizer?.gestureRecognizerFactories)) {
       return;
     }
@@ -118,20 +139,6 @@ class RenderAndroidView extends RenderBox {
     _gestureRecognizer = _AndroidViewGestureRecognizer(_motionEventsDispatcher, gestureRecognizers);
   }
 
-  static bool _factoryTypesSetEquals<T>(Set<Factory<T>> a, Set<Factory<T>> b) {
-    if (a == b) {
-      return true;
-    }
-    if (a == null ||  b == null) {
-      return false;
-    }
-    return setEquals(_factoriesTypeSet(a), _factoriesTypeSet(b));
-  }
-
-  static Set<Type> _factoriesTypeSet<T>(Set<Factory<T>> factories) {
-    return factories.map<Type>((Factory<T> factory) => factory.type).toSet();
-  }
-
   @override
   bool get sizedByParent => true;
 
@@ -244,30 +251,36 @@ class RenderAndroidView extends RenderBox {
 ///
 /// {@macro flutter.rendering.platformView.layout}
 ///
+/// {@macro flutter.rendering.platformView.gestures}
+///
 /// See also:
 ///  * [UiKitView] which is a widget that is used to show a UIView.
 ///  * [PlatformViewsService] which is a service for controlling platform views.
 class RenderUiKitView extends RenderBox {
   /// Creates a render object for an iOS UIView.
   ///
-  /// The `viewId` and `hitTestBehavior` parameters must not be null.
+  /// The `viewId`, `hitTestBehavior`, and `gestureRecognizers` parameters must not be null.
   RenderUiKitView({
-    @required int viewId,
+    @required UiKitViewController viewController,
     @required this.hitTestBehavior,
-  }) : assert(viewId != null),
+    @required Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers,
+  }) : assert(viewController != null),
        assert(hitTestBehavior != null),
-       _viewId = viewId;
+       assert(gestureRecognizers != null),
+       _viewController = viewController {
+    updateGestureRecognizers(gestureRecognizers);
+  }
 
 
   /// The unique identifier of the UIView controlled by this controller.
   ///
   /// Typically generated by [PlatformViewsRegistry.getNextPlatformViewId], the UIView
   /// must have been created by calling [PlatformViewsService.initUiKitView].
-  int get viewId => _viewId;
-  int _viewId;
-  set viewId(int viewId) {
+  UiKitViewController get viewController => _viewController;
+  UiKitViewController _viewController;
+  set viewController(UiKitViewController viewId) {
     assert(viewId != null);
-    _viewId = viewId;
+    _viewController = viewId;
     markNeedsPaint();
   }
 
@@ -276,6 +289,20 @@ class RenderUiKitView extends RenderBox {
   // any newly arriving events there's nothing we need to invalidate.
   PlatformViewHitTestBehavior hitTestBehavior;
 
+  /// {@macro flutter.rendering.platformView.updateGestureRecognizers}
+  void updateGestureRecognizers(Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers) {
+    assert(gestureRecognizers != null);
+    assert(
+    _factoriesTypeSet(gestureRecognizers).length == gestureRecognizers.length,
+    'There were multiple gesture recognizer factories for the same type, there must only be a single '
+        'gesture recognizer factory for each gesture recognizer type.',);
+    if (_factoryTypesSetEquals(gestureRecognizers, _gestureRecognizer?.gestureRecognizerFactories)) {
+      return;
+    }
+    _gestureRecognizer?.dispose();
+    _gestureRecognizer = _UiKitViewGestureRecognizer(viewController, gestureRecognizers);
+  }
+
   @override
   bool get sizedByParent => true;
 
@@ -285,6 +312,8 @@ class RenderUiKitView extends RenderBox {
   @override
   bool get isRepaintBoundary => true;
 
+  _UiKitViewGestureRecognizer _gestureRecognizer;
+
   @override
   void performResize() {
     size = constraints.biggest;
@@ -294,7 +323,7 @@ class RenderUiKitView extends RenderBox {
   void paint(PaintingContext context, Offset offset) {
     context.addLayer(PlatformViewLayer(
       rect: offset & size,
-      viewId: _viewId,
+      viewId: _viewController.id,
     ));
   }
 
@@ -308,16 +337,98 @@ class RenderUiKitView extends RenderBox {
 
   @override
   bool hitTestSelf(Offset position) => hitTestBehavior != PlatformViewHitTestBehavior.transparent;
+
+  @override
+  void handleEvent(PointerEvent event, HitTestEntry entry) {
+    if (event is PointerDownEvent) {
+      _gestureRecognizer.addPointer(event);
+    }
+  }
+
+  @override
+  void detach() {
+    _gestureRecognizer.reset();
+    super.detach();
+  }
+}
+
+// This recognizer constructs gesture recognizers from a set of gesture recognizer factories
+// it was give, adds all of them to a gesture arena team with the _UiKitViewGesturrRecognizer
+// as the team captain.
+// When the team wins a gesture the recognizer notifies the engine that it should release
+// the touch sequence to the embedded UIView.
+class _UiKitViewGestureRecognizer extends OneSequenceGestureRecognizer {
+  _UiKitViewGestureRecognizer(this.controller, this.gestureRecognizerFactories) {
+    team = GestureArenaTeam();
+    team.captain = this;
+    _gestureRecognizers = gestureRecognizerFactories.map(
+      (Factory<OneSequenceGestureRecognizer> recognizerFactory) {
+        return recognizerFactory.constructor()..team = team;
+      },
+    ).toSet();
+  }
+
+
+  // We use OneSequenceGestureRecognizers as they support gesture arena teams.
+  // TODO(amirh): get a list of GestureRecognizers here.
+  // https://github.com/flutter/flutter/issues/20953
+  final Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizerFactories;
+  Set<OneSequenceGestureRecognizer> _gestureRecognizers;
+
+  final UiKitViewController controller;
+
+  @override
+  void addPointer(PointerDownEvent event) {
+    startTrackingPointer(event.pointer);
+    for (OneSequenceGestureRecognizer recognizer in _gestureRecognizers) {
+      recognizer.addPointer(event);
+    }
+  }
+
+  @override
+  String get debugDescription => 'UIKit view';
+
+  @override
+  void didStopTrackingLastPointer(int pointer) {}
+
+  @override
+  void handleEvent(PointerEvent event) {
+    stopTrackingIfPointerNoLongerDown(event);
+  }
+
+  @override
+  void acceptGesture(int pointer) {
+    controller.acceptGesture();
+  }
+
+  @override
+  void rejectGesture(int pointer) {
+    // Currently the engine rejects the gesture when the sequence is done.
+    // This doesn't work well with gesture recognizers that recognize after the sequence
+    // has ended.
+    // TODO(amirh): trigger an engine gesture reject here.
+    // https://github.com/flutter/flutter/issues/24076
+  }
+
+  void reset() {
+    resolve(GestureDisposition.rejected);
+  }
 }
 
+// This recognizer constructs gesture recognizers from a set of gesture recognizer factories
+// it was give, adds all of them to a gesture arena team with the _AndroidViewGestureRecognizer
+// as the team captain.
+// As long as ta gesture arena is unresolved the recognizer caches all pointer events.
+// When the team wins the recognizer sends all the cached point events to the embedded Android view, and
+// sets itself to a "forwarding mode" where it will forward any new pointer event to the Android view.
 class _AndroidViewGestureRecognizer extends OneSequenceGestureRecognizer {
   _AndroidViewGestureRecognizer(this.dispatcher, this.gestureRecognizerFactories) {
     team = GestureArenaTeam();
     team.captain = this;
     _gestureRecognizers = gestureRecognizerFactories.map(
-      (Factory<OneSequenceGestureRecognizer> factory) {
-        return factory.constructor()..team = team;
-      }
+      (Factory<OneSequenceGestureRecognizer> recognizerFactory) {
+        return recognizerFactory.constructor()..team = team;
+      },
     ).toSet();
   }
 

packages/flutter/lib/src/services/platform_views.dart

@@ -617,6 +617,13 @@ class UiKitViewController {
     // TODO(amirh): invoke the iOS platform views channel direction method once available.
   }
 
+  Future<void> acceptGesture() {
+    final Map<String, dynamic> args = <String, dynamic> {
+      'id': id,
+    };
+    return SystemChannels.platform_views.invokeMethod('acceptGesture', args);
+  }
+
   /// Disposes the view.
   ///
   /// The [UiKitViewController] object is unusable after calling this.

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

@@ -26,11 +26,13 @@ import 'framework.dart';
 /// constraints.
 /// {@endtemplate}
 ///
-/// AndroidView participates in Flutter's [GestureArena]s, and dispatches touch events to the
-/// Android view iff it won the arena. Specific gestures that should be dispatched to the Android
-/// view can be specified in [AndroidView.gestureRecognizers]. If
-/// [AndroidView.gestureRecognizers] is empty, the gesture will be dispatched to the Android
+/// {@template flutter.widgets.platformViews.gestures}
+/// The widget participates in Flutter's [GestureArena]s, and dispatches touch events to the
+/// platform view iff it won the arena. Specific gestures that should be dispatched to the platform
+/// view can be specified in the `gestureRecognizers` constructor parameter. If
+/// the set of gesture recognizers is empty, a gesture will be dispatched to the platform
 /// view iff it was not claimed by any other gesture recognizer.
+/// {@endtemplate}
 ///
 /// The Android view object is created using a [PlatformViewFactory](/javadoc/io/flutter/plugin/platform/PlatformViewFactory.html).
 /// Plugins can register platform view factories with [PlatformViewRegistry#registerViewFactory](/javadoc/io/flutter/plugin/platform/PlatformViewRegistry.html#registerViewFactory-java.lang.String-io.flutter.plugin.platform.PlatformViewFactory-).
@@ -103,13 +105,15 @@ class AndroidView extends StatefulWidget {
 
   /// Which gestures should be forwarded to the Android view.
   ///
+  /// {@template flutter.widgets.platformViews.gestureRecognizersDescHead}
   /// The gesture recognizers built by factories in this set participate in the gesture arena for
   /// each pointer that was put down on the widget. If any of these recognizers win the
   /// gesture arena, the entire pointer event sequence starting from the pointer down event
-  /// will be dispatched to the Android view.
+  /// will be dispatched to the platform view.
   ///
   /// When null, an empty set of gesture recognizer factories is used, in which case a pointer event sequence
-  /// will only be dispatched to the Android view if no other member of the arena claimed it.
+  /// will only be dispatched to the platform view if no other member of the arena claimed it.
+  /// {@endtemplate}
   ///
   /// For example, with the following setup vertical drags will not be dispatched to the Android
   /// view as the vertical drag gesture is claimed by the parent [GestureDetector].
@@ -125,7 +129,7 @@ class AndroidView extends StatefulWidget {
   /// gesture recognizer factory in [gestureRecognizers] e.g:
   /// ```dart
   /// GestureDetector(
-  ///   onVerticalDragStart: (DragStartDetails d) {},
+  ///   onVerticalDragStart: (DragStartDetails details) {},
   ///   child: SizedBox(
   ///     width: 200.0,
   ///     height: 100.0,
@@ -141,7 +145,8 @@ class AndroidView extends StatefulWidget {
   /// )
   /// ```
   ///
-  /// An [AndroidView] can be configured to consume all pointers that were put down in its bounds
+  /// {@template flutter.widgets.platformViews.gestureRecognizersDescFoot}
+  /// A platform view can be configured to consume all pointers that were put down in its bounds
   /// by passing a factory for an [EagerGestureRecognizer] in [gestureRecognizers].
   /// [EagerGestureRecognizer] is a special gesture recognizer that immediately claims the gesture
   /// after a pointer down event.
@@ -149,7 +154,8 @@ class AndroidView extends StatefulWidget {
   /// The `gestureRecognizers` property must not contain more than one factory with the same [Factory.type].
   ///
   /// Changing `gestureRecognizers` results in rejection of any active gesture arenas (if the
-  /// Android view is actively participating in an arena).
+  /// platform view is actively participating in an arena).
+  /// {@endtemplate}
   // We use OneSequenceGestureRecognizers as they support gesture arena teams.
   // TODO(amirh): get a list of GestureRecognizers here.
   // https://github.com/flutter/flutter/issues/20953
@@ -180,7 +186,12 @@ class AndroidView extends StatefulWidget {
 ///
 /// {@macro flutter.widgets.platformViews.layout}
 ///
+/// {@macro flutter.widgets.platformViews.gestures}
+///
 /// {@macro flutter.widgets.platformViews.lifetime}
+///
+/// Construction of UIViews is done asynchronously, before the UIView is ready this widget paints
+/// nothing while maintaining the same layout constraints.
 class UiKitView extends StatefulWidget {
   /// Creates a widget that embeds an iOS view.
   ///
@@ -194,6 +205,7 @@ class UiKitView extends StatefulWidget {
     this.layoutDirection,
     this.creationParams,
     this.creationParamsCodec,
+    this.gestureRecognizers,
   }) : assert(viewType != null),
         assert(hitTestBehavior != null),
         assert(creationParams == null || creationParamsCodec != null),
@@ -227,6 +239,46 @@ class UiKitView extends StatefulWidget {
   /// This must not be null if [creationParams] is not null.
   final MessageCodec<dynamic> creationParamsCodec;
 
+  /// Which gestures should be forwarded to the UIKit view.
+  ///
+  /// {@macro flutter.widgets.platformViews.gestureRecognizersDescHead}
+  ///
+  /// For example, with the following setup vertical drags will not be dispatched to the UIKit
+  /// view as the vertical drag gesture is claimed by the parent [GestureDetector].
+  /// ```dart
+  /// GestureDetector(
+  ///   onVerticalDragStart: (DragStartDetails details) {},
+  ///   child: UiKitView(
+  ///     viewType: 'webview',
+  ///   ),
+  /// )
+  /// ```
+  /// To get the [UiKitView] to claim the vertical drag gestures we can pass a vertical drag
+  /// gesture recognizer factory in [gestureRecognizers] e.g:
+  /// ```dart
+  /// GestureDetector(
+  ///   onVerticalDragStart: (DragStartDetails details) {},
+  ///   child: SizedBox(
+  ///     width: 200.0,
+  ///     height: 100.0,
+  ///     child: UiKitView(
+  ///       viewType: 'webview',
+  ///       gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[
+  ///         new Factory<OneSequenceGestureRecognizer>(
+  ///           () => new EagerGestureRecognizer(),
+  ///         ),
+  ///       ].toSet(),
+  ///     ),
+  ///   ),
+  /// )
+  /// ```
+  ///
+  /// {@macro flutter.widgets.platformViews.gestureRecognizersDescFoot}
+  // We use OneSequenceGestureRecognizers as they support gesture arena teams.
+  // TODO(amirh): get a list of GestureRecognizers here.
+  // https://github.com/flutter/flutter/issues/20953
+  final Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers;
+
   @override
   State<UiKitView> createState() => _UiKitViewState();
 }
@@ -316,7 +368,6 @@ class _AndroidViewState extends State<AndroidView> {
 }
 
 class _UiKitViewState extends State<UiKitView> {
-  int _id;
   UiKitViewController _controller;
   TextDirection _layoutDirection;
   bool _initialized = false;
@@ -330,8 +381,9 @@ class _UiKitViewState extends State<UiKitView> {
       return const SizedBox.expand();
     }
     return _UiKitPlatformView(
-      viewId: _id,
+      controller: _controller,
       hitTestBehavior: widget.hitTestBehavior,
+      gestureRecognizers: widget.gestureRecognizers ?? _emptyRecognizersSet,
     );
   }
 
@@ -389,9 +441,9 @@ class _UiKitViewState extends State<UiKitView> {
   }
 
   Future<void> _createNewUiKitView() async {
-    _id = platformViewsRegistry.getNextPlatformViewId();
+    final int id = platformViewsRegistry.getNextPlatformViewId();
     final UiKitViewController controller = await PlatformViewsService.initUiKitView(
-      id: _id,
+      id: id,
       viewType: widget.viewType,
       layoutDirection: _layoutDirection,
       creationParams: widget.creationParams,
@@ -402,7 +454,7 @@ class _UiKitViewState extends State<UiKitView> {
       return;
     }
     if (widget.onPlatformViewCreated != null) {
-      widget.onPlatformViewCreated(_id);
+      widget.onPlatformViewCreated(id);
     }
     setState(() { _controller = controller; });
   }
@@ -442,26 +494,31 @@ class _AndroidPlatformView extends LeafRenderObjectWidget {
 class _UiKitPlatformView extends LeafRenderObjectWidget {
   const _UiKitPlatformView({
     Key key,
-    @required this.viewId,
+    @required this.controller,
     @required this.hitTestBehavior,
-  }) : assert(viewId != null),
+    @required this.gestureRecognizers,
+  }) : assert(controller != null),
        assert(hitTestBehavior != null),
+       assert(gestureRecognizers != null),
        super(key: key);
 
-  final int viewId;
+  final UiKitViewController controller;
   final PlatformViewHitTestBehavior hitTestBehavior;
+  final Set<Factory<OneSequenceGestureRecognizer>> gestureRecognizers;
 
   @override
   RenderObject createRenderObject(BuildContext context) {
     return RenderUiKitView(
-      viewId: viewId,
+      viewController: controller,
       hitTestBehavior: hitTestBehavior,
+      gestureRecognizers: gestureRecognizers,
     );
   }
 
   @override
   void updateRenderObject(BuildContext context, RenderUiKitView renderObject) {
-    renderObject.viewId = viewId;
+    renderObject.viewController = controller;
     renderObject.hitTestBehavior = hitTestBehavior;
+    renderObject.updateGestureRecognizers(gestureRecognizers);
   }
 }

packages/flutter/test/services/fake_platform_views.dart

@@ -159,6 +159,9 @@ class FakeIosPlatformViewsController {
   // delayed until it completes.
   Completer<void> creationDelay;
 
+  // Maps a view id to the number of gestures it accepted so fat.
+  final Map<int, int> gesturesAccepted = <int, int>{};
+
   void registerViewType(String viewType) {
     _registeredViewTypes.add(viewType);
   }
@@ -169,9 +172,11 @@ class FakeIosPlatformViewsController {
         return _create(call);
       case 'dispose':
         return _dispose(call);
+      case 'acceptGesture':
+        return _acceptGesture(call);
     }
     return Future<dynamic>.sync(() => null);
-    }
+  }
 
   Future<dynamic> _create(MethodCall call) async {
     if (creationDelay != null)
@@ -196,6 +201,14 @@ class FakeIosPlatformViewsController {
     }
 
     _views[id] = FakeUiKitView(id, viewType, creationParams);
+    gesturesAccepted[id] = 0;
+    return Future<int>.sync(() => null);
+  }
+
+  Future<dynamic> _acceptGesture(MethodCall call) async {
+    final Map<dynamic, dynamic> args = call.arguments;
+    final int id = args['id'];
+    gesturesAccepted[id] += 1;
     return Future<int>.sync(() => null);
   }
 

packages/flutter/test/widgets/platform_view_test.dart

@@ -999,5 +999,400 @@ void main() {
       );
     });
 
+    testWidgets('UiKitView accepts gestures', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: SizedBox(
+            width: 200.0,
+            height: 100.0,
+            child: UiKitView(viewType: 'webview', layoutDirection: TextDirection.ltr,),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 0);
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.up();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+    });
+
+    testWidgets('UiKitView transparent hit test behavior', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      int numPointerDownsOnParent = 0;
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Stack(
+            children: <Widget>[
+              Listener(
+                behavior: HitTestBehavior.opaque,
+                onPointerDown: (PointerDownEvent e) {
+                  numPointerDownsOnParent++;
+                },
+              ),
+              Positioned(
+                child: SizedBox(
+                  width: 200.0,
+                  height: 100.0,
+                  child: UiKitView(
+                    viewType: 'webview',
+                    hitTestBehavior: PlatformViewHitTestBehavior.transparent,
+                    layoutDirection: TextDirection.ltr,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.up();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 0);
+
+      expect(numPointerDownsOnParent, 1);
+    });
+
+    testWidgets('UiKitView translucent hit test behavior', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      int numPointerDownsOnParent = 0;
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Stack(
+            children: <Widget>[
+              Listener(
+                behavior: HitTestBehavior.opaque,
+                onPointerDown: (PointerDownEvent e) {
+                  numPointerDownsOnParent++;
+                },
+              ),
+              Positioned(
+                child: SizedBox(
+                  width: 200.0,
+                  height: 100.0,
+                  child: UiKitView(
+                    viewType: 'webview',
+                    hitTestBehavior: PlatformViewHitTestBehavior.translucent,
+                    layoutDirection: TextDirection.ltr,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.up();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+
+      expect(numPointerDownsOnParent, 1);
+    });
+
+    testWidgets('UiKitView opaque hit test behavior', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      int numPointerDownsOnParent = 0;
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Stack(
+            children: <Widget>[
+              Listener(
+                behavior: HitTestBehavior.opaque,
+                onPointerDown: (PointerDownEvent e) {
+                  numPointerDownsOnParent++;
+                },
+              ),
+              Positioned(
+                child: SizedBox(
+                  width: 200.0,
+                  height: 100.0,
+                  child: UiKitView(
+                    viewType: 'webview',
+                    hitTestBehavior: PlatformViewHitTestBehavior.opaque,
+                    layoutDirection: TextDirection.ltr,
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.up();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+      expect(numPointerDownsOnParent, 0);
+    });
+
+    testWidgets('UiKitView can lose gesture arenas', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      bool verticalDragAcceptedByParent = false;
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: Container(
+            margin: const EdgeInsets.all(10.0),
+            child: GestureDetector(
+              onVerticalDragStart: (DragStartDetails d) {
+                verticalDragAcceptedByParent = true;
+              },
+              child: SizedBox(
+                width: 200.0,
+                height: 100.0,
+                child: UiKitView(viewType: 'webview', layoutDirection: TextDirection.ltr),
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.moveBy(const Offset(0.0, 100.0));
+      await gesture.up();
+
+      expect(verticalDragAcceptedByParent, true);
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 0);
+    });
+
+    testWidgets('UiKitView gesture recognizers', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+      bool verticalDragAcceptedByParent = false;
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: GestureDetector(
+            onVerticalDragStart: (DragStartDetails d) {
+              verticalDragAcceptedByParent = true;
+            },
+            child: SizedBox(
+              width: 200.0,
+              height: 100.0,
+              child: UiKitView(
+                viewType: 'webview',
+                gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[
+                  Factory<VerticalDragGestureRecognizer>(
+                        () => VerticalDragGestureRecognizer(),
+                  ),
+                ].toSet(),
+                layoutDirection: TextDirection.ltr,
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.moveBy(const Offset(0.0, 100.0));
+      await gesture.up();
+
+      expect(verticalDragAcceptedByParent, false);
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+    });
+
+    testWidgets('UiKitView can claim gesture after all pointers are up', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+      bool verticalDragAcceptedByParent = false;
+      // The long press recognizer rejects the gesture after the AndroidView gets the pointer up event.
+      // This test makes sure that the Android view can win the gesture after it got the pointer up event.
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: GestureDetector(
+            onVerticalDragStart: (DragStartDetails d) {
+              verticalDragAcceptedByParent = true;
+            },
+            onLongPress: () {},
+            child: SizedBox(
+              width: 200.0,
+              height: 100.0,
+              child: UiKitView(
+                viewType: 'webview',
+                layoutDirection: TextDirection.ltr,
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.up();
+
+      expect(verticalDragAcceptedByParent, false);
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+    });
+
+    testWidgets('UiKitView rebuilt during gesture', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: SizedBox(
+            width: 200.0,
+            height: 100.0,
+            child: UiKitView(
+              viewType: 'webview',
+              layoutDirection: TextDirection.ltr,
+            ),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      final TestGesture gesture = await tester.startGesture(const Offset(50.0, 50.0));
+      await gesture.moveBy(const Offset(0.0, 100.0));
+
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: SizedBox(
+            width: 200.0,
+            height: 100.0,
+            child: UiKitView(
+              viewType: 'webview',
+              layoutDirection: TextDirection.ltr,
+            ),
+          ),
+        ),
+      );
+
+      await gesture.up();
+
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+    });
+
+    testWidgets('UiKitView with eager gesture recognizer', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+      await tester.pumpWidget(
+        Align(
+          alignment: Alignment.topLeft,
+          child: GestureDetector(
+            onVerticalDragStart: (DragStartDetails d) {},
+            child: SizedBox(
+              width: 200.0,
+              height: 100.0,
+              child: UiKitView(
+                viewType: 'webview',
+                gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[
+                  Factory<OneSequenceGestureRecognizer>(
+                        () => EagerGestureRecognizer(),
+                  ),
+                ].toSet(),
+                layoutDirection: TextDirection.ltr,
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // First frame is before the platform view was created so the render object
+      // is not yet in the tree.
+      await tester.pump();
+
+      await tester.startGesture(const Offset(50.0, 50.0));
+
+      // Normally (without the eager gesture recognizer) after just the pointer down event
+      // no gesture arena member will claim the arena (so no motion events will be dispatched to
+      // the Android view). Here we assert that with the eager recognizer in the gesture team the
+      // pointer down event is immediately dispatched.
+      expect(viewsController.gesturesAccepted[currentViewId + 1], 1);
+    });
+
+    testWidgets('AndroidView rebuilt with same gestureRecognizers', (WidgetTester tester) async {
+      final FakeIosPlatformViewsController viewsController = FakeIosPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      int factoryInvocationCount = 0;
+      final ValueGetter<EagerGestureRecognizer> constructRecognizer = () {
+        factoryInvocationCount += 1;
+        return EagerGestureRecognizer();
+      };
+
+      await tester.pumpWidget(
+        UiKitView(
+          viewType: 'webview',
+          gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[
+            Factory<EagerGestureRecognizer>(constructRecognizer),
+          ].toSet(),
+          layoutDirection: TextDirection.ltr,
+        ),
+      );
+
+      await tester.pumpWidget(
+        UiKitView(
+          viewType: 'webview',
+          hitTestBehavior: PlatformViewHitTestBehavior.translucent,
+          gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[
+            Factory<EagerGestureRecognizer>(constructRecognizer),
+          ].toSet(),
+          layoutDirection: TextDirection.ltr,
+        ),
+      );
+
+      expect(factoryInvocationCount, 1);
+    });
   });
 }