Fix for Android Visibility/Opacity crash (#785)

* Repro

* Fix for UI test

* Cache the Alpha value and queue up restoration after the visibility is changed

* Fix issue with negative height/width in UpdateLayout

* Clean up usings

2 files changed, 66 insertions, 0 deletions

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla51238.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla51238.cs
new file mode 100644
index 00000000..4bce76a0
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla51238.cs
@@ -0,0 +1,65 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 51238,
+		"Transparent Grid causes Java.Lang.IllegalStateException: Unable to create layer for Platform_DefaultRenderer",
+		PlatformAffected.Android)]
+	public class Bugzilla51238 : TestContentPage
+	{
+#if UITEST
+		[Test]
+		public void Issue1Test()
+		{
+			RunningApp.WaitForElement("Tap Me!");
+			RunningApp.Tap("Tap Me!"); // Crashes the app if the issue isn't fixed
+			RunningApp.WaitForElement("Tap Me!");
+		}
+#endif
+
+		protected override void Init()
+		{
+			var grid = new Grid();
+			grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+			grid.RowDefinitions.Add(new RowDefinition { Height = 50 });
+
+			var transparentLayer = new Grid();
+			transparentLayer.IsVisible = false;
+			transparentLayer.BackgroundColor = Color.Lime;
+			transparentLayer.Opacity = 0.5;
+
+			var label = new Label
+			{
+				Text = "Foo",
+				HorizontalOptions = LayoutOptions.Center,
+				VerticalOptions = LayoutOptions.Center
+			};
+
+			Grid.SetRow(label, 0);
+			Grid.SetRow(transparentLayer, 0);
+
+			var button = new Button
+			{
+				Text = "Tap Me!",
+				HorizontalOptions = LayoutOptions.Center,
+				VerticalOptions = LayoutOptions.Center
+			};
+
+			Grid.SetRow(button, 1);
+
+			button.Clicked += (sender, args) => { transparentLayer.IsVisible = !transparentLayer.IsVisible; };
+
+			grid.Children.Add(label);
+			grid.Children.Add(transparentLayer);
+			grid.Children.Add(button);
+
+			Content = grid;
+		}
+	}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
index 26f5bcbf..1093f1b0 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
@@ -171,6 +171,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla47923.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla48236.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla47971.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla51238.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla51642.xaml.cs">
       <DependentUpon>Bugzilla51642.xaml</DependentUpon>
       <SubType>Code</SubType>