1 files changed, 172 insertions, 0 deletions

diff --git a/Xamarin.Forms.Platform.Android/GestureManager.cs b/Xamarin.Forms.Platform.Android/GestureManager.cs
new file mode 100644
index 00000000..62d5db64
--- /dev/null
+++ b/Xamarin.Forms.Platform.Android/GestureManager.cs
@@ -0,0 +1,172 @@
+using System;
+using System.ComponentModel;
+using System.Linq;
+using Android.Support.V4.View;
+using Android.Views;
+
+namespace Xamarin.Forms.Platform.Android
+{
+	internal class GestureManager : IDisposable
+	{
+		IVisualElementRenderer _renderer;
+		readonly Lazy<GestureDetector> _tapAndPanDetector;
+		readonly Lazy<ScaleGestureDetector> _scaleDetector;
+
+		bool _disposed;
+		bool _inputTransparent;
+		bool _isEnabled;
+
+		VisualElement Element => _renderer?.Element;
+
+		View View => _renderer?.Element as View;
+
+		global::Android.Views.View Control => _renderer?.View;
+
+		public GestureManager(IVisualElementRenderer renderer)
+		{
+			_renderer = renderer;
+			_renderer.ElementChanged += OnElementChanged;
+
+			_tapAndPanDetector = new Lazy<GestureDetector>(InitializeTapAndPanDetector);
+			_scaleDetector = new Lazy<ScaleGestureDetector>(InitializeScaleDetector);
+		}
+
+		public bool OnTouchEvent(MotionEvent e)
+		{
+			if (Control == null)
+			{
+				return false;
+			}
+
+			if (!_isEnabled || _inputTransparent)
+			{
+				return false;
+			}
+
+			if (!DetectorsValid()) 
+			{
+				return false;
+			}
+
+			var eventConsumed = false;
+			if (ViewHasPinchGestures())
+			{
+				eventConsumed = _scaleDetector.Value.OnTouchEvent(e);
+			}
+
+			eventConsumed = _tapAndPanDetector.Value.OnTouchEvent(e) || eventConsumed;
+
+			return eventConsumed;
+		}
+
+		public void Dispose()
+		{
+			Dispose(true);
+			GC.SuppressFinalize(this);
+		}
+
+		bool DetectorsValid()
+		{
+			// Make sure we're not testing for gestures on old motion events after our 
+			// detectors have already been disposed
+
+			if (_scaleDetector.IsValueCreated && _scaleDetector.Value.Handle == IntPtr.Zero)
+			{
+				return false;
+			}
+
+			if (_tapAndPanDetector.IsValueCreated && _tapAndPanDetector.Value.Handle == IntPtr.Zero)
+			{
+				return false;
+			}
+
+			return true;
+		}
+
+		GestureDetector InitializeTapAndPanDetector()
+		{
+			var listener = new InnerGestureListener(new TapGestureHandler(() => View),
+				new PanGestureHandler(() => View, Control.Context.FromPixels));
+
+			return new GestureDetector(listener);
+		}
+
+		ScaleGestureDetector InitializeScaleDetector()
+		{
+			var listener = new InnerScaleListener(new PinchGestureHandler(() => View));
+			var detector = new ScaleGestureDetector(Control.Context, listener, Control.Handler);
+			ScaleGestureDetectorCompat.SetQuickScaleEnabled(detector, true);
+
+			return detector;
+		}
+
+		bool ViewHasPinchGestures()
+		{
+			return View != null && View.GestureRecognizers.OfType<PinchGestureRecognizer>().Any();
+		}
+
+		void OnElementChanged(object sender, VisualElementChangedEventArgs e)
+		{
+			if (e.OldElement != null)
+			{
+				e.OldElement.PropertyChanged -= OnElementPropertyChanged;
+			}
+
+			if (e.NewElement != null)
+			{
+                e.NewElement.PropertyChanged += OnElementPropertyChanged;
+			}
+
+			UpdateInputTransparent();
+			UpdateIsEnabled();
+		}
+
+		void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
+		{
+			if (e.PropertyName == VisualElement.InputTransparentProperty.PropertyName)
+				UpdateInputTransparent();
+			else if (e.PropertyName == VisualElement.IsEnabledProperty.PropertyName)
+				UpdateIsEnabled();
+		}
+
+		protected void Dispose(bool disposing)
+		{
+			if (_disposed)
+			{
+				return;
+			}
+
+			_disposed = true;
+
+			if (disposing)
+			{
+				if (Element != null)
+				{
+					Element.PropertyChanged -= OnElementPropertyChanged;
+				}
+
+				_renderer = null;
+			}
+		}
+
+		void UpdateInputTransparent()
+		{
+			if (Element == null)
+			{
+				return;
+			}
+
+			_inputTransparent = Element.InputTransparent;
+		}
+
+		void UpdateIsEnabled()
+		{
+			if (Element == null)
+			{
+				return;
+			}
+
+			_isEnabled = Element.IsEnabled;
+		}
+	}
+}
\ No newline at end of file