[Android] DatePicker unfocuses on cancel (#204)

The DatePicker in Android would remain focused when being closed via the
cancel button, and a subsequent re-focus via something such as button
would not function as expected.

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla41424.cs

@@ -0,0 +1,61 @@
+using System;
+
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 41424, "[Android] Clicking cancel on a DatePicker does not cause it to unfocus", PlatformAffected.Android)]
+	public class Bugzilla41424 : TestContentPage
+	{
+		const string DatePicker = "DatePicker";
+
+		protected override void Init()
+		{
+			var datePicker = new DatePicker
+			{
+				AutomationId = DatePicker
+			};
+			var datePickerFocusButton = new Button
+			{
+				Text = "Click to focus DatePicker",
+				Command = new Command(() => datePicker.Focus())
+			};
+			Content = new StackLayout
+			{
+				Children =
+				{
+					datePicker,
+					datePickerFocusButton
+				}
+			};
+		}
+
+#if UITEST
+
+#if __ANDROID__
+		[Test]
+		public void DatePickerCancelShouldUnfocus()
+		{
+			RunningApp.Tap(q => q.Marked(DatePicker));
+			RunningApp.WaitForElement(q => q.Marked("Cancel"));
+
+			RunningApp.Tap(q => q.Marked("Cancel"));
+			RunningApp.WaitForElement(q => q.Marked("Click to focus DatePicker"));
+
+			RunningApp.Tap(q => q.Marked("Click to focus DatePicker"));
+			RunningApp.WaitForElement(q => q.Marked("Cancel"));
+
+			RunningApp.Tap(q => q.Marked("Cancel"));
+		}
+#endif
+		
+#endif
+	}
+}

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

@@ -106,6 +106,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla31806.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41078.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40998.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41424.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34727.cs" />

Xamarin.Forms.Platform.Android/Renderers/DatePickerRenderer.cs

@@ -31,6 +31,7 @@ namespace Xamarin.Forms.Platform.Android
 				_disposed = true;
 				if (_dialog != null)
 				{
+					_dialog.CancelEvent -= OnCancelButtonClicked;
 					_dialog.Hide();
 					_dialog.Dispose();
 					_dialog = null;
@@ -84,6 +85,7 @@ namespace Xamarin.Forms.Platform.Android
 				_dialog.Hide();
 				((IElementController)Element).SetValueFromRenderer(VisualElement.IsFocusedPropertyKey, false);
 				Control.ClearFocus();
+				_dialog.CancelEvent -= OnCancelButtonClicked;
 				_dialog = null;
 			}
 		}
@@ -96,6 +98,8 @@ namespace Xamarin.Forms.Platform.Android
 				view.Date = e.Date;
 				((IElementController)view).SetValueFromRenderer(VisualElement.IsFocusedPropertyKey, false);
 				Control.ClearFocus();
+
+				_dialog.CancelEvent -= OnCancelButtonClicked;
 				_dialog = null;
 			}, year, month, day);
 		}
@@ -123,9 +127,16 @@ namespace Xamarin.Forms.Platform.Android
 
 			UpdateMinimumDate();
 			UpdateMaximumDate();
+
+			_dialog.CancelEvent += OnCancelButtonClicked;
 			_dialog.Show();
 		}
 
+		void OnCancelButtonClicked(object sender, EventArgs e)
+		{
+			Element.Unfocus();
+		}
+
 		void SetDate(DateTime date)
 		{
 			Control.Text = date.ToString(Element.Format);