[Android] Handle rapid taps when only single-tap recognizer is present (#1188)

* Handle rapid tapping correctly

* Remove failed optimization attempt for 2-pointer gestures

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla59863_0.cs

@@ -0,0 +1,92 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.Gestures)]
+#endif
+
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 59863, "TapGestureRecognizer extremely finicky", PlatformAffected.Android)]
+	public class Bugzilla59863_0 : TestContentPage
+	{
+		int _singleTaps;
+		const string SingleTapBoxId = "singleTapView";
+
+		const string Singles = "singles(s)";
+
+		protected override void Init()
+		{
+			var instructions = new Label
+			{
+				Text = "Tap the box below several times quickly. " 
+				+ "The number displayed below should match the number of times you tap the box."
+			};
+
+			var singleTapCounter = new Label {Text = $"{_singleTaps} {Singles}"};
+			
+			var singleTapBox = new BoxView
+			{
+				WidthRequest = 100,
+				HeightRequest = 100,
+				BackgroundColor = Color.Bisque,
+				AutomationId = SingleTapBoxId
+			};
+
+			var singleTap = new TapGestureRecognizer
+			{
+				Command = new Command(() =>
+				{
+					_singleTaps = _singleTaps + 1;
+					singleTapCounter.Text = $"{_singleTaps} {Singles} on {SingleTapBoxId}";
+				})
+			};
+
+			singleTapBox.GestureRecognizers.Add(singleTap);
+
+			Content = new StackLayout
+			{
+				Margin = 40,
+				HorizontalOptions = LayoutOptions.Fill, VerticalOptions = LayoutOptions.Fill,
+				Children = { instructions, singleTapBox, singleTapCounter }
+			};
+		}
+
+#if UITEST
+		[Test] 
+		public void TapsCountShouldMatch()
+		{
+			// Gonna add this test because we'd want to know if it _did_ start failing
+			// But it doesn't really help much with this issue; UI test can't tap fast enough to demonstrate the 
+			// problem we're trying to solve
+
+			int tapsToTest = 5;
+
+			RunningApp.WaitForElement(SingleTapBoxId);
+
+			for (int n = 0; n < tapsToTest; n++)
+			{
+				RunningApp.Tap(SingleTapBoxId);
+			}
+
+			RunningApp.WaitForElement($"{tapsToTest} {Singles} on {SingleTapBoxId}");
+		}
+
+		[Test]
+		public void DoubleTapWithOnlySingleTapRecognizerShouldRegisterTwoTaps()
+		{
+			RunningApp.WaitForElement(SingleTapBoxId);
+			RunningApp.DoubleTap(SingleTapBoxId);
+
+			RunningApp.WaitForElement($"2 {Singles} on {SingleTapBoxId}");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla59863_1.cs

@@ -0,0 +1,84 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.Gestures)]
+#endif
+
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 59863, "TapGestureRecognizer extremely finicky", PlatformAffected.Android, 
+		issueTestNumber:1)]
+	public class Bugzilla59863_1 : TestContentPage
+	{
+		int _doubleTaps;
+		const string DoubleTapBoxId = "doubleTapView";
+
+		const string Doubles = "double(s)";
+
+		protected override void Init()
+		{
+			var instructions = new Label
+			{
+				Text = "Tap the box below once. The counter should not increment. " 
+						+ "Double tap the box. The counter should increment."
+			};
+
+			var doubleTapCounter = new Label {Text = $"{_doubleTaps} {Doubles} on {DoubleTapBoxId}"};
+
+			var doubleTapBox = new BoxView
+			{
+				WidthRequest = 100,
+				HeightRequest = 100,
+				BackgroundColor = Color.Chocolate,
+				AutomationId = DoubleTapBoxId
+			};
+
+			var doubleTap = new TapGestureRecognizer
+			{
+				NumberOfTapsRequired = 2,
+				Command = new Command(() =>
+				{
+					_doubleTaps = _doubleTaps + 1;
+					doubleTapCounter.Text = $"{_doubleTaps} {Doubles} on {DoubleTapBoxId}";
+				})
+			};
+
+			doubleTapBox.GestureRecognizers.Add(doubleTap);
+
+			Content = new StackLayout
+			{	
+				Margin = 40,
+				HorizontalOptions = LayoutOptions.Fill, VerticalOptions = LayoutOptions.Fill,
+				Children = { instructions, doubleTapBox, doubleTapCounter }
+			};
+		}
+
+#if UITEST
+		[Test]
+		public void SingleTapWithOnlyDoubleTapRecognizerShouldRegisterNothing()
+		{
+			RunningApp.WaitForElement(DoubleTapBoxId);
+			RunningApp.Tap(DoubleTapBoxId);
+
+			RunningApp.WaitForElement($"0 {Doubles} on {DoubleTapBoxId}");
+		}
+
+		[Test]
+		public void DoubleTapWithOnlyDoubleTapRecognizerShouldRegisterOneDoubleTap()
+		{
+			RunningApp.WaitForElement(DoubleTapBoxId);
+			RunningApp.DoubleTap(DoubleTapBoxId);
+
+			RunningApp.WaitForElement($"1 {Doubles} on {DoubleTapBoxId}");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla59863_2.cs

@@ -0,0 +1,99 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.Gestures)]
+#endif
+
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 59863, "TapGestureRecognizer extremely finicky", PlatformAffected.Android, 
+		issueTestNumber: 2)]
+	public class Bugzilla59863_2 : TestContentPage
+	{
+		int _mixedSingleTaps;
+		int _mixedDoubleTaps;
+		const string MixedTapBoxId = "mixedTapView";
+
+		const string Singles = "singles(s)";
+		const string Doubles = "double(s)";
+
+		protected override void Init()
+		{
+			var instructions = new Label
+			{
+				Text = "Tap the box below once. The single tap counter should increment. " 
+				+ "Double tap the box. The double tap counter should increment, " 
+				+ "but the single tap counter should not."
+			};
+
+			var mixedSingleTapCounter = new Label {Text = $"{_mixedSingleTaps} {Singles}"};
+			var mixedDoubleTapCounter = new Label {Text = $"{_mixedDoubleTaps} {Doubles}"};
+
+			var mixedTapBox = new BoxView
+			{
+				WidthRequest = 100,
+				HeightRequest = 100,
+				BackgroundColor = Color.Coral,
+				AutomationId = MixedTapBoxId
+			};
+
+			var mixedDoubleTap = new TapGestureRecognizer
+			{
+				NumberOfTapsRequired = 2,
+				Command = new Command(() =>
+				{
+					_mixedDoubleTaps = _mixedDoubleTaps + 1;
+					mixedDoubleTapCounter.Text = $"{_mixedDoubleTaps} {Doubles} on {MixedTapBoxId}";
+				})
+			};
+
+			var mixedSingleTap = new TapGestureRecognizer
+			{
+				NumberOfTapsRequired = 1,
+				Command = new Command(() =>
+				{
+					_mixedSingleTaps = _mixedSingleTaps + 1;
+					mixedSingleTapCounter.Text = $"{_mixedSingleTaps} {Singles} on {MixedTapBoxId}";
+				})
+			};
+
+			mixedTapBox.GestureRecognizers.Add(mixedDoubleTap);
+			mixedTapBox.GestureRecognizers.Add(mixedSingleTap);
+
+			Content = new StackLayout
+			{	
+				Margin = 40,
+				HorizontalOptions = LayoutOptions.Fill, VerticalOptions = LayoutOptions.Fill,
+				Children = { instructions, mixedTapBox, mixedSingleTapCounter, mixedDoubleTapCounter }
+			};
+		}
+
+#if UITEST
+		[Test]
+		public void DoubleTapWithMixedRecognizersShouldRegisterDoubleTap()
+		{
+			RunningApp.WaitForElement(MixedTapBoxId);
+			RunningApp.DoubleTap(MixedTapBoxId);
+
+			RunningApp.WaitForElement($"1 {Doubles} on {MixedTapBoxId}");
+		}
+
+		[Test]
+		public void SingleTapWithMixedRecognizersShouldRegisterSingleTap()
+		{
+			RunningApp.WaitForElement(MixedTapBoxId);
+			RunningApp.Tap(MixedTapBoxId);
+
+			RunningApp.WaitForElement($"1 {Singles} on {MixedTapBoxId}");
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -218,6 +218,12 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla57910.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla58406.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla58833.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla51427.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59248.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59580.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59863_0.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59863_1.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59863_2.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ButtonBackgroundColorTest.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />

Xamarin.Forms.Platform.Android/InnerGestureListener.cs

@@ -61,7 +61,20 @@ namespace Xamarin.Forms.Platform.Android
 			if (_disposed)
 				return false;
 
-			return _tapDelegate(2);
+			if (HasDoubleTapHandler())
+			{
+				return _tapDelegate(2);
+			}
+
+			if (HasSingleTapHandler())
+			{
+				// If we're registering double taps and we don't actually have a double-tap handler,
+				// but we _do_ have a single-tap handler, then we're really just seeing two singles in a row
+				// Fire off the delegate for the second single-tap (OnSingleTapUp already did the first one)
+				return _tapDelegate(1);
+			}
+
+			return false;
 		}
 
 		bool GestureDetector.IOnDoubleTapListener.OnDoubleTapEvent(MotionEvent e)
@@ -134,7 +147,7 @@ namespace Xamarin.Forms.Platform.Android
 
 			if (!HasDoubleTapHandler())
 			{
-				// We're not worried about double-tap, so OnSingleTap has already run the delegate
+				// We're not worried about double-tap, so OnSingleTapUp has already run the delegate
 				// there's nothing for us to do here
 				return false;
 			}
@@ -201,5 +214,12 @@ namespace Xamarin.Forms.Platform.Android
 				return false;
 			return _tapGestureRecognizers(2).Any();
 		}
+
+		bool HasSingleTapHandler()
+		{
+			if (_tapGestureRecognizers == null)
+				return false;
+			return _tapGestureRecognizers(1).Any();
+		}
 	}
 }