1 files changed, 109 insertions, 0 deletions
diff --git a/Xamarin.Forms.Platform.iOS/Renderers/KeyboardInsetTracker.cs b/Xamarin.Forms.Platform.iOS/Renderers/KeyboardInsetTracker.cs
new file mode 100644
index 00000000..d5759947
--- /dev/null
+++ b/Xamarin.Forms.Platform.iOS/Renderers/KeyboardInsetTracker.cs
@@ -0,0 +1,109 @@
+using System;
+using System.Drawing;
+#if __UNIFIED__
+using UIKit;
+#else
+using MonoTouch.UIKit;
+#endif
+#if __UNIFIED__
+using RectangleF = CoreGraphics.CGRect;
+using SizeF = CoreGraphics.CGSize;
+using PointF = CoreGraphics.CGPoint;
+
+#else
+using nfloat=System.Single;
+using nint=System.Int32;
+using nuint=System.UInt32;
+#endif
+
+namespace Xamarin.Forms.Platform.iOS
+{
+	internal class KeyboardInsetTracker : IDisposable
+	{
+		readonly Func<UIWindow> _fetchWindow;
+		readonly Action<PointF> _setContentOffset;
+		readonly Action<UIEdgeInsets> _setInsetAction;
+		readonly UIView _targetView;
+		bool _disposed;
+
+		RectangleF _lastKeyboardRect;
+
+		public KeyboardInsetTracker(UIView targetView, Func<UIWindow> fetchWindow, Action<UIEdgeInsets> setInsetAction) : this(targetView, fetchWindow, setInsetAction, null)
+		{
+		}
+
+		public KeyboardInsetTracker(UIView targetView, Func<UIWindow> fetchWindow, Action<UIEdgeInsets> setInsetAction, Action<PointF> setContentOffset)
+		{
+			_setContentOffset = setContentOffset;
+			_targetView = targetView;
+			_fetchWindow = fetchWindow;
+			_setInsetAction = setInsetAction;
+			KeyboardObserver.KeyboardWillShow += OnKeyboardShown;
+			KeyboardObserver.KeyboardWillHide += OnKeyboardHidden;
+		}
+
+		public void Dispose()
+		{
+			if (_disposed)
+				return;
+			_disposed = true;
+
+			KeyboardObserver.KeyboardWillShow -= OnKeyboardShown;
+			KeyboardObserver.KeyboardWillHide -= OnKeyboardHidden;
+		}
+
+		//This method allows us to update the insets if the Frame changes
+		internal void UpdateInsets()
+		{
+			//being called from LayoutSubviews but keyboard wasn't shown yet
+			if (_lastKeyboardRect.IsEmpty)
+				return;
+
+			var window = _fetchWindow();
+			// Code left verbose to make its operation more obvious
+			if (window == null)
+			{
+				// we are not currently displayed and can safely ignore this
+				// most likely this renderer is on a page which is currently not displayed (e.g. in NavController)
+				return;
+			}
+
+			var field = _targetView.FindFirstResponder();
+
+			//the view that is triggering the keyboard is not inside our UITableView?
+			//if (field == null)
+			//	return;
+
+			var boundsSize = _targetView.Frame.Size;
+
+			//since our keyboard frame is RVC CoordinateSpace, lets convert it to our targetView CoordinateSpace
+			var rect = _targetView.Superview.ConvertRectFromView(_lastKeyboardRect, null);
+			//let's see how much does it cover our target view
+			var overlay = RectangleF.Intersect(rect, _targetView.Frame);
+
+			_setInsetAction(new UIEdgeInsets(0, 0, overlay.Height, 0));
+
+			if (field is UITextView && _setContentOffset != null)
+			{
+				var keyboardTop = boundsSize.Height - overlay.Height;
+				var fieldPosition = field.ConvertPointToView(field.Frame.Location, _targetView.Superview);
+				var fieldBottom = fieldPosition.Y + field.Frame.Height;
+				var offset = fieldBottom - keyboardTop;
+				if (offset > 0)
+					_setContentOffset(new PointF(0, offset));
+			}
+		}
+
+		void OnKeyboardHidden(object sender, UIKeyboardEventArgs args)
+		{
+			_setInsetAction(new UIEdgeInsets(0, 0, 0, 0));
+			_lastKeyboardRect = RectangleF.Empty;
+		}
+
+		void OnKeyboardShown(object sender, UIKeyboardEventArgs args)
+		{
+			_lastKeyboardRect = args.FrameEnd;
+			UpdateInsets();
+		}
+	}
+}
+\ No newline at end of file