1 files changed, 68 insertions, 0 deletions
diff --git a/Xamarin.Forms.Platform.Android/InnerScaleListener.cs b/Xamarin.Forms.Platform.Android/InnerScaleListener.cs
new file mode 100644
index 00000000..4a6c6581
--- /dev/null
+++ b/Xamarin.Forms.Platform.Android/InnerScaleListener.cs
@@ -0,0 +1,68 @@
+using System;
+using Android.Runtime;
+using Android.Views;
+
+namespace Xamarin.Forms.Platform.Android
+{
+	internal class InnerScaleListener : ScaleGestureDetector.SimpleOnScaleGestureListener
+	{
+		Func<float, Point, bool> _pinchDelegate;
+		Action _pinchEndedDelegate;
+		Func<Point, bool> _pinchStartedDelegate;
+
+		public InnerScaleListener(Func<float, Point, bool> pinchDelegate, Func<Point, bool> pinchStarted, Action pinchEnded)
+		{
+			if (pinchDelegate == null)
+				throw new ArgumentNullException("pinchDelegate");
+
+			if (pinchStarted == null)
+				throw new ArgumentNullException("pinchStarted");
+
+			if (pinchEnded == null)
+				throw new ArgumentNullException("pinchEnded");
+
+			_pinchDelegate = pinchDelegate;
+			_pinchStartedDelegate = pinchStarted;
+			_pinchEndedDelegate = pinchEnded;
+		}
+
+		// This is needed because GestureRecognizer callbacks can be delayed several hundred milliseconds
+		// which can result in the need to resurect this object if it has already been disposed. We dispose
+		// eagerly to allow easier garbage collection of the renderer
+		internal InnerScaleListener(IntPtr handle, JniHandleOwnership ownership) : base(handle, ownership)
+		{
+		}
+
+		public override bool OnScale(ScaleGestureDetector detector)
+		{
+			float cur = detector.CurrentSpan;
+			float last = detector.PreviousSpan;
+
+			if (Math.Abs(cur - last) < 10)
+				return false;
+
+			return _pinchDelegate(detector.ScaleFactor, new Point(Forms.Context.FromPixels(detector.FocusX), Forms.Context.FromPixels(detector.FocusY)));
+		}
+
+		public override bool OnScaleBegin(ScaleGestureDetector detector)
+		{
+			return _pinchStartedDelegate(new Point(Forms.Context.FromPixels(detector.FocusX), Forms.Context.FromPixels(detector.FocusY)));
+		}
+
+		public override void OnScaleEnd(ScaleGestureDetector detector)
+		{
+			_pinchEndedDelegate();
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing)
+			{
+				_pinchDelegate = null;
+				_pinchStartedDelegate = null;
+				_pinchEndedDelegate = null;
+			}
+			base.Dispose(disposing);
+		}
+	}
+}
+\ No newline at end of file