[Android] CarouselView problems updating ObservableCollection (#7693) fixes #7678

* Fixed 7678: [Android] CarouselView binded to a new ObservableCollection filled with Items does not render content

* Added test instructions

* Fixed build error

* Updated sample model name

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7678.cs

@@ -0,0 +1,141 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.CarouselView)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 7678, "[Android] CarouselView binded to a new ObservableCollection filled with Items does not render content", PlatformAffected.Android)]
+	public class Issue7678Droid : TestContentPage
+	{
+		public Issue7678Droid()
+		{
+			Title = "Issue 7678";
+			BindingContext = new Issue7678DroidViewModel();
+		}
+
+		protected override void Init()
+		{
+			var layout = new StackLayout();
+
+			var instructions = new Label
+			{
+				Margin = new Thickness(6),
+				Text = "The CarouselView below must show items. If you do not see any item, this test has failed."
+			};
+
+			var itemsLayout =
+				new LinearItemsLayout(ItemsLayoutOrientation.Horizontal)
+				{
+					SnapPointsType = SnapPointsType.MandatorySingle,
+					SnapPointsAlignment = SnapPointsAlignment.Center
+				};
+
+			var carouselView = new CarouselView
+			{
+				ItemsLayout = itemsLayout,
+				ItemTemplate = GetCarouselTemplate()
+			};
+
+			carouselView.SetBinding(ItemsView.ItemsSourceProperty, "Items");
+
+			layout.Children.Add(instructions);
+			layout.Children.Add(carouselView);
+
+			Content = layout;
+		}
+
+		protected override async void OnAppearing()
+		{
+			base.OnAppearing();
+
+			await ((Issue7678DroidViewModel)BindingContext).LoadItemsAsync();
+		}
+
+		internal DataTemplate GetCarouselTemplate()
+		{
+			return new DataTemplate(() =>
+			{
+				var grid = new Grid();
+
+				var info = new Label
+				{
+					HorizontalOptions = LayoutOptions.Center,
+					VerticalOptions = LayoutOptions.Center,
+					Margin = new Thickness(6)
+				};
+
+				info.SetBinding(Label.TextProperty, new Binding("Name"));
+
+				grid.Children.Add(info);
+
+				var frame = new Frame
+				{
+					Content = grid,
+					HasShadow = false
+				};
+
+				frame.SetBinding(BackgroundColorProperty, new Binding("Color"));
+
+				return frame;
+			});
+		}
+	}
+
+	[Preserve(AllMembers = true)]
+	public class Issue7678DroidModel
+	{
+		public Color Color { get; set; }
+		public string Name { get; set; }
+	}
+
+	[Preserve(AllMembers = true)]
+	public class Issue7678DroidViewModel : BindableObject
+	{
+		ObservableCollection<Issue7678DroidModel> _items;
+  
+		public ObservableCollection<Issue7678DroidModel> Items
+		{
+			get { return _items; }
+			set
+			{
+				_items = value;
+				OnPropertyChanged();
+			}
+		}
+
+		public async Task LoadItemsAsync()
+		{
+			Items = new ObservableCollection<Issue7678DroidModel>();
+
+			var random = new Random();
+			var items = new List<Issue7678DroidModel>();
+
+			for (int n = 0; n < 5; n++)
+			{
+				items.Add(new Issue7678DroidModel
+				{
+					Color = Color.FromRgb(random.Next(0, 255), random.Next(0, 255), random.Next(0, 255)),
+					Name = $"{n + 1}"
+				});
+			}
+
+			await Task.Delay(500);
+
+			_items = new ObservableCollection<Issue7678DroidModel>(items);
+			OnPropertyChanged(nameof(Items));
+		}
+	}
+}

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

@@ -1074,6 +1074,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue7395.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7582.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7563.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue7678.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla22229.xaml">
@@ -1443,19 +1444,19 @@
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7621.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7512.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue5354.xaml">
       <SubType>Designer</SubType>
-      <Generator>MSBuild:Compile</Generator>
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
 </Project>

Xamarin.Forms.Platform.Android/CollectionView/CarouselViewRenderer.cs

@@ -54,7 +54,9 @@ namespace Xamarin.Forms.Platform.Android
 
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs changedProperty)
 		{
-			if (changedProperty.Is(CarouselView.PeekAreaInsetsProperty))
+			if (changedProperty.Is(ItemsView.ItemsSourceProperty))
+				UpdateItemsSource();
+			else if (changedProperty.Is(CarouselView.PeekAreaInsetsProperty))
 				UpdatePeekAreaInsets();
 			else if (changedProperty.Is(CarouselView.IsSwipeEnabledProperty))
 				UpdateIsSwipeEnabled();