[iOS] CollectionView not applying "Selected" VisualState to pre-selec…

…ted items (#14672)

* Fix issue setting initial selected VisualState in iOS CollectionView

* Updated the issue steps

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue14513.xaml

@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<local:TestContentPage
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:d="http://xamarin.com/schemas/2014/forms/design"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    Title="Test 14513" xmlns:local="using:Xamarin.Forms.Controls"
+    x:Class="Xamarin.Forms.Controls.Issues.Issue14513">
+    <StackLayout
+        Padding="12">
+        <Label
+            Text="If the selected item have a Red background, the test has passed."/>
+        <CollectionView
+            ItemsSource="{Binding Items}"
+            SelectedItem="{Binding SelectedItem}"
+            SelectionMode="Single">
+            <CollectionView.ItemTemplate>
+                <DataTemplate>
+                    <Grid>
+                        <VisualStateManager.VisualStateGroups>
+                            <VisualStateGroup Name="CommonStates">
+                                <VisualState Name="Normal" />
+                                <VisualState Name="Selected">
+                                    <VisualState.Setters>
+                                        <Setter Property="BackgroundColor" Value="Red" />
+                                    </VisualState.Setters>
+                                </VisualState>
+                            </VisualStateGroup>
+                        </VisualStateManager.VisualStateGroups>
+                        <Label
+                            x:Name="Title"
+                            Text="{Binding Name}"
+                            FontSize="Large" />
+                    </Grid>
+                </DataTemplate>
+            </CollectionView.ItemTemplate>
+        </CollectionView>
+    </StackLayout>
+</local:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue14513.xaml.cs

@@ -0,0 +1,68 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System.Collections.ObjectModel;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.CollectionView)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 14513,
+		"[Bug] [iOS] SelectedItems custom image not displaying in iOS for CollectionView until tapped",
+		PlatformAffected.iOS)]
+	public partial class Issue14513 : TestContentPage
+	{
+		public Issue14513()
+		{
+#if APP
+			InitializeComponent();
+#endif
+		}
+
+		protected override void Init()
+		{
+			BindingContext = new Issue14513ViewModel();
+		}
+	}
+
+	public class Issue14513Model
+	{
+		public string Name { get; set; }
+	}
+
+	public class Issue14513ViewModel : BindableObject
+	{
+		Issue14513Model _selectedItem;
+
+		public Issue14513ViewModel()
+		{
+			Items = new ObservableCollection<Issue14513Model>
+			{
+				new Issue14513Model { Name = "Item 1" },
+				new Issue14513Model { Name = "Item 2" },
+				new Issue14513Model { Name = "Item 3" }
+			};
+
+			SelectedItem = Items[1];
+		}
+
+		public ObservableCollection<Issue14513Model> Items { get; set; }
+
+		public Issue14513Model SelectedItem
+		{
+			get { return _selectedItem; }
+			set
+			{
+				_selectedItem = value;
+				OnPropertyChanged();
+			}
+		}
+	}
+}

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

@@ -1827,6 +1827,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue13577.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14505.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14505-II.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue14513.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue6387.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14757.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14897.xaml.cs" />
@@ -2354,6 +2355,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue13577.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue14513.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue6387.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>

Xamarin.Forms.Platform.iOS/CollectionView/TemplatedCell.cs

@@ -175,6 +175,8 @@ void SetRenderer(IVisualElementRenderer renderer)
 
 			InitializeContentConstraints(nativeView);
 
+			UpdateVisualStates();
+
 			renderer.Element.MeasureInvalidated += MeasureInvalidated;
 		}
 
@@ -246,15 +248,7 @@ public override bool Selected
 			set
 			{
 				base.Selected = value;
-
-				var element = VisualElementRenderer?.Element;
-
-				if (element != null)
-				{
-					VisualStateManager.GoToState(element, value
-						? VisualStateManager.CommonStates.Selected
-						: VisualStateManager.CommonStates.Normal);
-				}
+				UpdateVisualStates();
 			}
 		}
 
@@ -304,5 +298,17 @@ bool SizesAreSame(CGSize preferredSize, Size elementSize)
 
 			return true;
 		}
+
+		void UpdateVisualStates()
+		{
+			var element = VisualElementRenderer?.Element;
+
+			if (element != null)
+			{
+				VisualStateManager.GoToState(element, Selected
+					? VisualStateManager.CommonStates.Selected
+					: VisualStateManager.CommonStates.Normal);
+			}
+		}
 	}
 }