[Android] propagate elevation after initial elevation changes android (#6271)

fixes #6262

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue6262.cs

@@ -0,0 +1,93 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Text;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 6262, "[Bug] Button in Grid gets wrong z-index",
+		PlatformAffected.iOS)]
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.Layout)]
+#endif
+	public class Issue6262 : TestContentPage
+	{
+		protected override void Init()
+		{
+			Grid theGrid = null;
+			theGrid = new Grid() { VerticalOptions = LayoutOptions.FillAndExpand };
+			SetupGrid(theGrid);
+
+			Content = new StackLayout()
+			{
+				Children =
+				{
+					theGrid,
+					new Button()
+					{
+						Text = "Click this and see if test succeeds. If you don't see failure text then test has passed",
+						AutomationId = "RetryTest",
+						Command = new Command(() => SetupGrid(theGrid))
+					}
+				}
+			};
+
+		}
+
+		void SetupGrid(Grid theGrid)
+		{
+			if(theGrid.Children.Count > 0)
+				theGrid.Children.Clear();
+
+			theGrid.Children.Add(
+				new Button()
+				{
+					HorizontalOptions = LayoutOptions.Fill,
+					VerticalOptions = LayoutOptions.Fill,
+					Text = "If you can see this the test has failed",
+					AutomationId = "ClickMe",
+					Command = new Command(() =>
+					{
+						theGrid.Children.Clear();
+						theGrid.Children.Add(new Label() { AutomationId = "Fail", Text = "Test Failed" });
+					})
+				});
+
+			theGrid.Children.Add(
+				new Image()
+				{
+					Source = "coffee.png",
+					HorizontalOptions = LayoutOptions.Fill,
+					VerticalOptions = LayoutOptions.Fill,
+					AutomationId = "ClickMe",
+					BackgroundColor = Color.Green
+				});
+		}
+
+#if UITEST
+		[Test]
+		public void ImageShouldLayoutOnTopOfButton()
+		{
+			RunningApp.WaitForElement("ClickMe");
+			RunningApp.Tap("ClickMe");
+			RunningApp.WaitForElement("ClickMe");
+			RunningApp.WaitForNoElement("Fail");
+			RunningApp.Tap("RetryTest");
+			RunningApp.WaitForElement("ClickMe");
+			RunningApp.Tap("ClickMe");
+			RunningApp.WaitForElement("ClickMe");
+			RunningApp.WaitForNoElement("Fail");
+		}
+#endif
+	}
+}

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

@@ -9,6 +9,7 @@
     <Import_RootNamespace>Xamarin.Forms.Controls.Issues</Import_RootNamespace>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="$(MSBuildThisFileDirectory)Issue6262.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla59172.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue5766.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue4684.xaml.cs" />
@@ -1205,4 +1206,4 @@
       <DependentUpon>Issue6130.xaml</DependentUpon>
     </Compile>
   </ItemGroup>
-</Project>
+</Project>

Xamarin.Forms.Core.UITests.Shared/UITestCategories.cs

@@ -19,6 +19,7 @@
 		public const string Image = "Image";
 		public const string ImageButton = "ImageButton";
 		public const string Label = "Label";
+		public const string Layout = "Layout";
 		public const string ListView = "ListView";
 		public const string UwpIgnore = "UwpIgnore";
 		public const string LifeCycle = "Lifecycle";

Xamarin.Forms.Platform.Android/Platform.cs

@@ -1183,7 +1183,7 @@ namespace Xamarin.Forms.Platform.Android
 
 		#endregion
 
-		internal class DefaultRenderer : VisualElementRenderer<View>
+		internal class DefaultRenderer : VisualElementRenderer<View>, ILayoutChanges
 		{
 			public bool NotReallyHandled { get; private set; }
 			IOnTouchListener _touchListener;

Xamarin.Forms.Platform.Android/VisualElementPackager.cs

@@ -37,6 +37,21 @@ namespace Xamarin.Forms.Platform.Android
 
 			_renderer = renderer;
 			_renderer.ElementChanged += OnElementChanged;
+
+			if(renderer.View is ILayoutChanges layout)
+				layout.LayoutChange += OnInitialLayoutChange;
+		}
+
+		void OnInitialLayoutChange(object sender, AView.LayoutChangeEventArgs e)
+		{
+			// this is used to adjust any relative elevations on the child elements that still need to settle
+			// the default elevation is set on Button after it's already added to the view hierarchy
+			// but this appears to only be the case when the app first starts
+
+			if (sender is ILayoutChanges layout)
+				layout.LayoutChange -= OnInitialLayoutChange;
+
+			EnsureChildOrder(true);
 		}
 
 		void OnElementChanged(object sender, VisualElementChangedEventArgs e)
@@ -80,6 +95,10 @@ namespace Xamarin.Forms.Platform.Android
 
 					_renderer.Element.ChildrenReordered -= _childReorderedHandler;
 				}
+
+				if (_renderer.View is ILayoutChanges layout)
+					layout.LayoutChange -= OnInitialLayoutChange;
+
 				_renderer = null;
 			}
 
@@ -141,7 +160,10 @@ namespace Xamarin.Forms.Platform.Android
 				Performance.Stop(reference);
 			}
 		}
-		void EnsureChildOrder()
+
+		void EnsureChildOrder() => EnsureChildOrder(false);
+
+		void EnsureChildOrder(bool onlyUpdateElevations)
 		{
 			float elevationToSet = 0;
 			for (var i = 0; i < ElementController.LogicalChildren.Count; i++)
@@ -162,12 +184,13 @@ namespace Xamarin.Forms.Platform.Android
 							{
 								if (elevation > elevationToSet)
 									elevationToSet = elevation;
-
+																
 								r.View.Elevation = elevationToSet;
 							}
 						}
 
-						(_renderer.View as ViewGroup)?.BringChildToFront(r.View);
+						if(!onlyUpdateElevations)
+							(_renderer.View as ViewGroup)?.BringChildToFront(r.View);
 					}
 				}
 			}

Xamarin.Forms.Sandbox.Android/Xamarin.Forms.Sandbox.Android.csproj

@@ -93,7 +93,6 @@
     <Folder Include="Resources\drawable-xhdpi\" />
     <Folder Include="Resources\drawable-xxhdpi\" />
     <Folder Include="Resources\drawable-xxxhdpi\" />
-    <Folder Include="Resources\drawable\" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Stubs\Xamarin.Forms.Platform.Android\Xamarin.Forms.Platform.Android (Forwarders).csproj">
@@ -121,6 +120,12 @@
       <Name>Xamarin.Forms.Sandbox</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <AndroidResource Include="Resources\drawable\coffee.png">
+      <Generator>MSBuild:UpdateGeneratedFiles</Generator>
+      <SubType>Designer</SubType>
+    </AndroidResource>
+  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\Android\Xamarin.Android.CSharp.targets" />
   <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$(SolutionDir)\.nuget\NuGet.targets')" />
 </Project>