[Android, iOS] Fix CarouselView Issues (#7366)

* Fixed CarouselViewGalleries sample on Android

* Protect NRE setting the CurrentItem

* Fixed issue changing the ItemsSource

* Fixed issues with NumberOfSideItems and PeekAreaInsects properties on Android

* Fixed formatting

* Fix ItemSpacing issue on Android

* Fixed vertical peek insets iOS

* Center item after change ItemSpacing
Improve IsSwipeEnabled logic on Android (disable swipe but not touch)

* Update max slider value when item count is updated

* Update CarouselCodeGallery.cs

* NoOfSideItems in test page

Xamarin.Forms.ControlGallery.Android/Xamarin.Forms.ControlGallery.Android.csproj

@@ -163,6 +163,7 @@
     <AndroidResource Include="Resources\drawable\booksflyout.png" />
     <AndroidResource Include="Resources\drawable\homeflyout.png" />
     <AndroidResource Include="Resources\drawable\xamarinlogo.png" />
+    <AndroidResource Include="Resources\drawable\cardBackground.png" />
   </ItemGroup>
   <ItemGroup>
     <AndroidResource Include="Resources\drawable\Icon.png" />

Xamarin.Forms.Controls/CoreGalleryPages/CarouselViewCoreGalleryPage.cs

@@ -8,6 +8,8 @@ namespace Xamarin.Forms.Controls
 	[Preserve(AllMembers = true)]
 	internal class CarouselViewCoreGalleryPage : CoreGalleryPage<CarouselView>
 	{
+		private object _currentItem;
+
 		protected override void InitializeElement(CarouselView element)
 		{
 			base.InitializeElement(element);
@@ -23,15 +25,19 @@ namespace Xamarin.Forms.Controls
 		{
 			base.Build(stackLayout);
 
+			var currentItemContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.CurrentItem, new CarouselView { HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate(), CurrentItem = _currentItem }, "CurrentItem", value => value.ToString());
 			var isSwipeEnabledContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.IsSwipeEnabled, new CarouselView { IsSwipeEnabled = false, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate()}, "IsSwipeEnabled", value => value.ToString());
 			var isScrollAnimatedContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.IsScrollAnimated, new CarouselView { IsScrollAnimated = false, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate() }, "IsScrollAnimated", value => value.ToString());
-			var numberOfSideItemsContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.NumberOfSideItems, new CarouselView { NumberOfSideItems = 2, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate() }, "NumberOfSideItems", value => value.ToString());
+			var horizontalNumberOfSideItemsContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.NumberOfSideItems, new CarouselView { NumberOfSideItems = 2, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate() }, "NumberOfSideItems", value => value.ToString());
+			var verticalNumberOfSideItemsContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.NumberOfSideItems, new CarouselView { NumberOfSideItems = 2, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Vertical), ItemTemplate = GetCarouselTemplate() }, "NumberOfSideItems", value => value.ToString());
 			var peekAreaInsetsContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.PeekAreaInsets, new CarouselView { PeekAreaInsets = new Thickness(24, 12, 36, 6), HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate() }, "PeekAreaInsets", value => value.ToString());
 			var positionContainer = new ValueViewContainer<CarouselView>(Test.CarouselView.Position, new CarouselView { Position = 2, HeightRequest = 250, ItemsSource = GetCarouselItems(), ItemsLayout = GetCarouselLayout(ItemsLayoutOrientation.Horizontal), ItemTemplate = GetCarouselTemplate() }, "Position", value => value.ToString());
 
+			Add(currentItemContainer);
 			Add(isSwipeEnabledContainer);
 			Add(isScrollAnimatedContainer);
-			Add(numberOfSideItemsContainer);
+			Add(horizontalNumberOfSideItemsContainer);
+			Add(verticalNumberOfSideItemsContainer);
 			Add(peekAreaInsetsContainer);
 			Add(positionContainer);
 		}
@@ -51,6 +57,8 @@ namespace Xamarin.Forms.Controls
 				});
 			}
 
+			_currentItem = items[5];
+
 			return items;
 		}
 

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/CarouselCodeGallery.cs

@@ -1,10 +1,11 @@
-using System.Collections;
-using Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.SpacingGalleries;
+using Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.SpacingGalleries;
+using Xamarin.Forms.Internals;
 using Xamarin.Forms.PlatformConfiguration;
 using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
 
 namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries
 {
+	[Preserve(AllMembers = true)]
 	internal class CarouselCodeGallery : ContentPage
 	{
 		readonly Label _scrollInfoLabel = new Label();
@@ -46,13 +47,17 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 				ItemsLayout = itemsLayout,
 				ItemTemplate = itemTemplate,
 				Position = 2,
-			//	NumberOfSideItems = 1,
+				//NumberOfSideItems = 1,
 				Margin = new Thickness(0,10,0,40),
-				PeekAreaInsets = new Thickness(30,0,30,0),
 				BackgroundColor = Color.LightGray,
 				AutomationId = "TheCarouselView"
 			};
 
+			if (orientation == ItemsLayoutOrientation.Horizontal)
+				carouselView.PeekAreaInsets = new Thickness(30, 0, 30, 0);
+			else
+				carouselView.PeekAreaInsets = new Thickness(0, 30, 0, 30);
+
 			carouselView.Scrolled += CarouselView_Scrolled;
 
 			layout.Children.Add(carouselView);
@@ -78,12 +83,18 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 			{
 				Maximum = 100,
 				Minimum = 0,
-				Value = 30
+				Value = 30,
+				WidthRequest = 100,
+				BackgroundColor = Color.Pink
 			};
 
 			padi.ValueChanged += (s, e) => {
 				var peek = padi.Value;
-				carouselView.PeekAreaInsets = new Thickness(peek, 0, peek, 0);
+
+				if (orientation == ItemsLayoutOrientation.Horizontal)
+					carouselView.PeekAreaInsets = new Thickness(peek, 0, peek, 0);
+				else
+					carouselView.PeekAreaInsets = new Thickness(0, peek, 0, peek);
 			};
 
 			stckPeek.Children.Add(padi);
@@ -107,7 +118,8 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 		{
 			_scrollInfoLabel.Text = $"First item: {e.FirstVisibleItemIndex}, Last item: {e.LastVisibleItemIndex}";
 
-			double delta = 0, offset = 0;
+			double delta;
+			double offset;
 
 			if (_orientation == ItemsLayoutOrientation.Horizontal)
 			{

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/CarouselViewGallery.cs

@@ -1,5 +1,8 @@
-namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries
 {
+	[Preserve(AllMembers = true)]
 	internal class CarouselViewGallery : ContentPage
 	{
 		public CarouselViewGallery()

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/CarouselXamlGallery.xaml

@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<ContentPage xmlns:gallery="clr-namespace:Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries.CarouselXamlGallery">
+<ContentPage
+    xmlns:gallery="clr-namespace:Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries.CarouselXamlGallery"
+    Title="CarouselView Xaml">
     <Grid Margin="0,50,00,0">
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto" />

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/CarouselXamlGallery.xaml.cs

@@ -1,10 +1,10 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using Xamarin.Forms;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries
 {
+	[Preserve(AllMembers = true)]
 	public partial class CarouselXamlGallery : ContentPage
 	{
 		public CarouselXamlGallery()
@@ -15,12 +15,14 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 		}
 	}
 
+	[Preserve(AllMembers = true)]
 	public enum CarouselXamlSampleType
 	{
 		Normal,
 		Peek
 	}
 
+	[Preserve(AllMembers = true)]
 	internal class CarouselViewModel : ViewModelBase2
 	{
 		int _count;
@@ -76,6 +78,7 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 		}
 	}
 
+	[Preserve(AllMembers = true)]
 	internal class CarouselItem
 	{
 		public CarouselItem(int index, string image = null)

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/ExampleTemplateCarousel.xaml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<Grid Padding="10,0,10,0" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries.ExampleTemplateCarousel">
+<Grid Padding="10,0,10,0" xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries.ExampleTemplateCarousel">
     <VisualStateManager.VisualStateGroups>
         <VisualStateGroup x:Name="CarouselViewStates">
             <VisualState x:Name="CurrentItem">
@@ -29,7 +30,7 @@
             </VisualState>
         </VisualStateGroup>
     </VisualStateManager.VisualStateGroups>
-    <Frame x:Name="frame" HasShadow="True" Padding="0" HorizontalOptions="Center" VerticalOptions="Center">
+    <Frame x:Name="frame" HasShadow="True" Padding="0" HorizontalOptions="Center" VerticalOptions="Center" BackgroundColor="Yellow">
         <Image Source="{Binding FeaturedImage}" InputTransparent="true" Aspect="AspectFit" />
     </Frame>
 </Grid>

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/CarouselViewGalleries/ExampleTemplateCarousel.xaml.cs

@@ -1,16 +1,16 @@
 using System;
-using System.Collections.Generic;
-using Xamarin.Forms;
+using Xamarin.Forms.Internals;
 
 namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselViewGalleries
 {
-	public partial class ExampleTemplateCarousel
+	[Preserve(AllMembers = true)]
+	public partial class ExampleTemplateCarousel : Grid
 	{
-		double initialY = -1;
-		bool delete;
-		double maxYScroll = 300;
-		double diffYScroll = -150;
-		double minYScroll = -30;
+		double _initialY = -1;
+		bool _delete;
+		readonly double _maxYScroll = 300;
+		readonly double _diffYScroll = -150;
+		readonly double _minYScroll = -30;
 
 		public ExampleTemplateCarousel()
 		{
@@ -22,41 +22,41 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries.CarouselVi
 			{
 				if (e.StatusType == GestureStatus.Started)
 				{
-					initialY = Y;
+					_initialY = Y;
 				}
 
 				if (e.StatusType == GestureStatus.Running)
 				{
-					if (e.TotalY < minYScroll)
+					if (e.TotalY < _minYScroll)
 					{
-						var scaledValue = 1 - (Math.Abs(e.TotalY) / maxYScroll);
+						var scaledValue = 1 - (Math.Abs(e.TotalY) / _maxYScroll);
 						this.ScaleTo(0.9);
 						this.FadeTo(scaledValue);
 						this.TranslateTo(X, Y + e.TotalY);
 					}
-					if (e.TotalY < diffYScroll)
+					if (e.TotalY < _diffYScroll)
 					{
-						delete = true;
+						_delete = true;
 					}
 				}
 
 				if (e.StatusType == GestureStatus.Completed || e.StatusType == GestureStatus.Canceled)
 				{
-					if (delete)
+					if (_delete)
 					{
 						this.FadeTo(0.1);
 						this.TranslateTo(X, Y - 1000);
-						MessagingCenter.Send<ExampleTemplateCarousel>(this, "remove");
+						MessagingCenter.Send(this, "remove");
 					}
 					else
 					{
 						this.ScaleTo(1);
 						this.FadeTo(1);
-						this.TranslateTo(X, initialY);
+						this.TranslateTo(X, _initialY);
 					}
 				}
 			};
 			GestureRecognizers.Add(gesture);
 		}
 	}
-}
+}

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/ItemsSourceGenerator.cs

@@ -20,8 +20,11 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries
 		readonly ItemsView _cv;
 		private readonly ItemsSourceType _itemsSourceType;
 		readonly Entry _entry;
+		readonly Entry _entrySideItems;
 		int _count = 0;
 
+		CarouselView carousel => _cv as CarouselView;
+
 		public int Count => _count;
 		public ItemsSourceGenerator(ItemsView cv, int initialItems = 1000, 
 			ItemsSourceType itemsSourceType = ItemsSourceType.List)
@@ -36,11 +39,15 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries
 			};
 
 			var button = new Button { Text = "Update", AutomationId = "btnUpdate"  };
-			var label = new Label { Text = "Item count:", VerticalTextAlignment = TextAlignment.Center };
-			_entry = new Entry { Keyboard = Keyboard.Numeric, Text = initialItems.ToString(), WidthRequest = 200, AutomationId = "entryUpdate" };
+			var label = new Label { Text = "Items:", VerticalTextAlignment = TextAlignment.Center };
+			var labelSideItems = new Label { Text = "Side items:", VerticalTextAlignment = TextAlignment.Center };
+			_entry = new Entry { Keyboard = Keyboard.Numeric, Text = initialItems.ToString(), WidthRequest = 100, AutomationId = "entryUpdate" };
+			_entrySideItems = new Entry { Keyboard = Keyboard.Numeric, Text = carousel?.NumberOfSideItems.ToString(), WidthRequest = 100, AutomationId = "entrySideItemsUpdate" };
 
 			layout.Children.Add(label);
 			layout.Children.Add(_entry);
+			layout.Children.Add(labelSideItems);
+			layout.Children.Add(_entrySideItems);
 			layout.Children.Add(button);
 
 			button.Clicked += GenerateItems;
@@ -108,14 +115,15 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries
 				}
 
 				_obsCollection = new ObservableCollection<CollectionViewGalleryTestItem>(items);
-				_obsCollection.CollectionChanged += ObsItemsSource_CollectionChanged;
+				_count = _obsCollection.Count;
+				CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+
 				_cv.ItemsSource = _obsCollection;
 			}
 		}
 
 		void ObsItemsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
 		{
-			_count = _obsCollection.Count;
 			CollectionChanged?.Invoke(sender, e);
 		}
 
@@ -157,6 +165,12 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries
 		void GenerateItems(object sender, EventArgs e)
 		{
 			GenerateItems();
+
+			if (carousel == null)
+				return;
+
+			if (int.TryParse(_entrySideItems.Text, out int count))
+				carousel.NumberOfSideItems = count;
 		}
 	}
 }

Xamarin.Forms.Controls/GalleryPages/CollectionViewGalleries/PositionControl.cs

@@ -73,7 +73,8 @@ namespace Xamarin.Forms.Controls.GalleryPages.CollectionViewGalleries
 
 		public void UpdatePositionCount(int itemsCount)
 		{
-			_slider.Maximum = itemsCount - 1;
+			if (itemsCount > 0)
+				_slider.Maximum = itemsCount - 1;
 
 		}
 	}

Xamarin.Forms.Core/Items/CarouselView.cs

@@ -72,7 +72,7 @@ namespace Xamarin.Forms
 		}
 
 		public static readonly BindableProperty CurrentItemProperty =
-		BindableProperty.Create(nameof(CurrentItem), typeof(object), typeof(CarouselView), default(object),
+		BindableProperty.Create(nameof(CurrentItem), typeof(object), typeof(CarouselView), default, BindingMode.TwoWay, 
 			propertyChanged: CurrentItemPropertyChanged);
 
 		public static readonly BindableProperty CurrentItemChangedCommandProperty =
@@ -124,7 +124,6 @@ namespace Xamarin.Forms
 			carouselView.OnCurrentItemChanged(args);
 		}
 
-
 		public static readonly BindableProperty PositionProperty =
 		BindableProperty.Create(nameof(Position), typeof(int), typeof(CarouselView), default(int), BindingMode.TwoWay,
 			propertyChanged: PositionPropertyChanged);
@@ -205,9 +204,9 @@ namespace Xamarin.Forms
 
 		static int GetPositionForItem(CarouselView carouselView, object item)
 		{
-			var itemSource = carouselView.ItemsSource as IList;
+			var itemSource = carouselView?.ItemsSource as IList;
 
-			for (int n = 0; n < itemSource.Count; n++)
+			for (int n = 0; n < itemSource?.Count; n++)
 			{
 				if (itemSource[n] == item)
 				{

Xamarin.Forms.CustomAttributes/TestAttributes.cs

@@ -862,6 +862,7 @@ namespace Xamarin.Forms.CustomAttributes
 
 		public enum CarouselView
 		{
+			CurrentItem,
 			IsSwipeEnabled,
 			IsScrollAnimated,
 			NumberOfSideItems, 

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

@@ -7,37 +7,71 @@ namespace Xamarin.Forms.Platform.Android
 {
 	internal class CarouselSpacingItemDecoration : RecyclerView.ItemDecoration
 	{
-		readonly IItemsLayout _itemsLayout;
-		readonly Func<int> _getWidth;
-		readonly Func<int> _getHeight;
+		readonly ItemsLayoutOrientation _orientation;
+		readonly double _verticalSpacing;
+		double _adjustedVerticalSpacing = -1;
+		readonly double _horizontalSpacing;
+		double _adjustedHorizontalSpacing = -1;
 
-		public CarouselSpacingItemDecoration(IItemsLayout itemsLayout, Func<int> getWidth, Func<int> getHeight)
+		public CarouselSpacingItemDecoration(IItemsLayout itemsLayout)
 		{
-			_itemsLayout = itemsLayout;
-			_getWidth = getWidth;
-			_getHeight = getHeight;
+			var layout = itemsLayout ?? throw new ArgumentNullException(nameof(itemsLayout));
+
+			switch (layout)
+			{
+				case GridItemsLayout gridItemsLayout:
+					_orientation = gridItemsLayout.Orientation;
+					_horizontalSpacing = gridItemsLayout.HorizontalItemSpacing;
+					_verticalSpacing = gridItemsLayout.VerticalItemSpacing;
+					break;
+				case ListItemsLayout listItemsLayout:
+					_orientation = listItemsLayout.Orientation;
+					if (_orientation == ItemsLayoutOrientation.Horizontal)
+						_horizontalSpacing = listItemsLayout.ItemSpacing;
+					else
+						_verticalSpacing = listItemsLayout.ItemSpacing;
+					break;
+			}
+		}
+
+		public override void OnDraw(Canvas c, RecyclerView parent, RecyclerView.State state)
+		{
+			base.OnDraw(c, parent, state);
 		}
 
 		public override void GetItemOffsets(Rect outRect, AView view, RecyclerView parent, RecyclerView.State state)
 		{
 			base.GetItemOffsets(outRect, view, parent, state);
 
+			if (Math.Abs(_adjustedVerticalSpacing - (-1)) < double.Epsilon)
+			{
+				_adjustedVerticalSpacing = parent.Context.ToPixels(_verticalSpacing);
+			}
+
+			if (Math.Abs(_adjustedHorizontalSpacing - (-1)) < double.Epsilon)
+			{
+				_adjustedHorizontalSpacing = parent.Context.ToPixels(_horizontalSpacing);
+			}
+
 			int position = parent.GetChildAdapterPosition(view);
 			int itemCount = state.ItemCount;
-			int width = _getWidth();
 
 			if (position == RecyclerView.NoPosition || itemCount == 0)
 				return;
 
-			// this is the first and last item , we need to give them some inset 
-			if (position == 0)
-				outRect.Left = width / itemCount;
+			if (_orientation == ItemsLayoutOrientation.Vertical)
+			{
+				outRect.Left = position == 0 ? 0 : (int)_adjustedHorizontalSpacing;
+				outRect.Bottom = (int)(_adjustedVerticalSpacing - (_verticalSpacing * 2));
+				outRect.Top = (int)(_adjustedVerticalSpacing - (_verticalSpacing * 2));
+			}
 
-			if (position == itemCount - 1)
-				outRect.Right = width;
-
-			if (position == itemCount)
-				outRect.Left = width;
+			if (_orientation == ItemsLayoutOrientation.Horizontal)
+			{
+				outRect.Top = position == 0 ? 0 : (int)_adjustedVerticalSpacing;
+				outRect.Right = (int)(_adjustedHorizontalSpacing - (_horizontalSpacing * 2));
+				outRect.Left = (int)(_adjustedHorizontalSpacing - (_horizontalSpacing * 2));
+			}
 		}
 	}
 }

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

@@ -1,31 +1,37 @@
 using System;
 using System.ComponentModel;
 using Android.Content;
-using Android.Support.V7.Widget;
 using Android.Views;
+using FormsCollectionView = Xamarin.Forms.CollectionView;
 
 namespace Xamarin.Forms.Platform.Android
 {
 	public class CarouselViewRenderer : ItemsViewRenderer<ItemsView, ItemsViewAdapter<ItemsView, IItemsViewSource>, IItemsViewSource>
 	{
-		readonly Context _context;
 		protected CarouselView Carousel;
+		IItemsLayout _layout;
+		ItemDecoration _itemDecoration;
 		bool _isSwipeEnabled;
 		bool _isUpdatingPositionFromForms;
 		int _oldPosition;
 		int _initialPosition;
-		bool _scrollingToInitialPosition = true;
 
 		public CarouselViewRenderer(Context context) : base(context)
 		{
-			_context = context;
+			FormsCollectionView.VerifyCollectionViewFlagEnabled(nameof(CarouselViewRenderer));
 		}
 
 		protected override void Dispose(bool disposing)
 		{
 			if (disposing)
 			{
+				if (_itemDecoration != null)
+				{
+					_itemDecoration.Dispose();
+					_itemDecoration = null;
+				}
 
+				_layout = null;
 			}
 
 			base.Dispose(disposing);
@@ -42,9 +48,11 @@ namespace Xamarin.Forms.Platform.Android
 			}
 
 			Carousel = newElement as CarouselView;
+			_layout = ItemsView.ItemsLayout;
 
 			UpdateIsSwipeEnabled();
 			UpdateInitialPosition();
+			UpdateItemSpacing();
 		}
 
 		protected override void UpdateItemsSource()
@@ -52,47 +60,42 @@ namespace Xamarin.Forms.Platform.Android
 			// By default the CollectionViewAdapter creates the items at whatever size the template calls for
 			// But for the Carousel, we want it to create the items to fit the width/height of the viewport
 			// So we give it an alternate delegate for creating the views
-
-			ItemsViewAdapter = new ItemsViewAdapter<ItemsView, IItemsViewSource>(ItemsView, 
-				(view, context) => new SizedItemContentView(context, () => Width, () => Height));
+			ItemsViewAdapter = new ItemsViewAdapter<ItemsView, IItemsViewSource>(ItemsView,
+				(view, context) => new SizedItemContentView(Context, GetItemWidth, GetItemHeight));
 
 			SwapAdapter(ItemsViewAdapter, false);
 		}
 
-		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
+		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs changedProperty)
 		{
-			if (e.Is(CarouselView.IsSwipeEnabledProperty))
+			if (changedProperty.Is(CarouselView.PeekAreaInsetsProperty))
+				Tracker?.UpdateLayout();
+			else if (changedProperty.Is(CarouselView.IsSwipeEnabledProperty))
 				UpdateIsSwipeEnabled();
-			else if (e.Is(CarouselView.IsBounceEnabledProperty))
+			else if (changedProperty.Is(CarouselView.IsBounceEnabledProperty))
 				UpdateIsBounceEnabled();
+			else if (changedProperty.Is(ListItemsLayout.ItemSpacingProperty))
+				UpdateItemSpacing();
 		}
 
-		public override bool OnTouchEvent(MotionEvent e)
+		public override bool OnInterceptTouchEvent(MotionEvent ev)
 		{
-			//TODO: this doesn't work because we need to interact with the Views
 			if (!_isSwipeEnabled)
-			{
 				return false;
-			}
-			return base.OnTouchEvent(e);
+			
+			return base.OnInterceptTouchEvent(ev);
 		}
 
 		public override void OnScrollStateChanged(int state)
 		{
 			base.OnScrollStateChanged(state);
 
-			System.Diagnostics.Debug.WriteLine($"State {state}");
-
 			if (_isSwipeEnabled)
 			{
 				if (state == ScrollStateDragging)
-				{
 					Carousel.SetIsDragging(true);
-				}
 				else
-				{
 					Carousel.SetIsDragging(false);
-				}
 			}
 		}
 
@@ -105,7 +108,59 @@ namespace Xamarin.Forms.Platform.Android
 
 		protected override ItemDecoration CreateSpacingDecoration(IItemsLayout itemsLayout)
 		{
-			return new CarouselSpacingItemDecoration(itemsLayout, GetItemWidth, GetItemHeight);
+			return new CarouselSpacingItemDecoration(itemsLayout);
+		}
+
+		protected override void UpdateItemSpacing()
+		{
+			if (_layout == null)
+			{
+				return;
+			}
+
+			if (_itemDecoration != null)
+			{
+				RemoveItemDecoration(_itemDecoration);
+			}
+
+			_itemDecoration = CreateSpacingDecoration(_layout);
+			AddItemDecoration(_itemDecoration);
+
+			var adapter = GetAdapter();
+
+			if (adapter != null)
+			{
+				adapter.NotifyItemChanged(_oldPosition);
+				Carousel.ScrollTo(_oldPosition, position: Xamarin.Forms.ScrollToPosition.Center);
+			}
+
+			base.UpdateItemSpacing();
+		}
+
+		int GetItemWidth()
+		{
+			var itemWidth = Width;
+
+			if (_layout is ListItemsLayout listItemsLayout && listItemsLayout.Orientation == ItemsLayoutOrientation.Horizontal)
+			{
+				var numberOfVisibleItems = Carousel.NumberOfSideItems * 2 + 1;
+				itemWidth = (int)(Width - Carousel.PeekAreaInsets.Left - Carousel.PeekAreaInsets.Right - Context?.ToPixels(listItemsLayout.ItemSpacing)) / numberOfVisibleItems;
+			}
+
+			return itemWidth;
+		}
+
+		int GetItemHeight()
+		{
+			var itemHeight = Height;
+
+			if (_layout is ListItemsLayout listItemsLayout && listItemsLayout.Orientation == ItemsLayoutOrientation.Vertical)
+			{
+				var numberOfVisibleItems = Carousel.NumberOfSideItems * 2 + 1;
+				itemHeight = (int)(Height - Carousel.PeekAreaInsets.Top - Carousel.PeekAreaInsets.Bottom - Context?.ToPixels(listItemsLayout.ItemSpacing)) / numberOfVisibleItems;
+			}
+
+			return itemHeight;
 		}
 
 		void UpdateIsSwipeEnabled()
@@ -118,12 +173,12 @@ namespace Xamarin.Forms.Platform.Android
 			if (position == -1 || _isUpdatingPositionFromForms)
 				return;
 
-			var context = ItemsViewAdapter?.ItemsSource.GetItem(position);
+			var item = ItemsViewAdapter?.ItemsSource.GetItem(position);
 
-			if (context == null)
+			if (item == null)
 				throw new InvalidOperationException("Visible item not found");
 
-			Carousel.SetCurrentItem(context);
+			Carousel.SetCurrentItem(item);
 		}
 
 		void UpdateIsBounceEnabled()
@@ -131,26 +186,6 @@ namespace Xamarin.Forms.Platform.Android
 			OverScrollMode = Carousel.IsBounceEnabled ? OverScrollMode.Always : OverScrollMode.Never;
 		}
 
-		int GetItemWidth()
-		{
-			var numberofSideItems = (Element as CarouselView).NumberOfSideItems;
-			var numberOfItems = numberofSideItems * 2 + 1;
-			int spacingWidth = 0;
-
-			if (Carousel.ItemsLayout is ListItemsLayout listItemsLayout && numberofSideItems > 0)
-				spacingWidth = (int)listItemsLayout.ItemSpacing * (numberOfItems - 1);
-
-			var itemWidth = (Width - (int)Context.ToPixels(spacingWidth)) / numberOfItems;
-
-			return itemWidth;
-		}
-
-		int GetItemHeight()
-		{ 	 
-			//TODO: Calculate item height.
-			return Height;
-		}
-
 		void UpdatePositionFromScroll()
 		{
 			var snapHelper = GetSnapManager()?.GetCurrentSnapHelper();
@@ -165,12 +200,7 @@ namespace Xamarin.Forms.Platform.Android
 			if (snapView != null)
 			{
 				int middleCenterPosition = layoutManager.GetPosition(snapView);
-				if (_scrollingToInitialPosition)
-				{
-					_scrollingToInitialPosition = !(_initialPosition == middleCenterPosition);
-					return;
-				}
-
+	
 				if (_oldPosition != middleCenterPosition)
 				{
 					_oldPosition = middleCenterPosition;
@@ -182,8 +212,9 @@ namespace Xamarin.Forms.Platform.Android
 		void UpdateInitialPosition()
 		{
 			_isUpdatingPositionFromForms = true;
-			//Goto to the Correct Position
+			// Goto to the Correct Position
 			_initialPosition = Carousel.Position;
+			_oldPosition = _initialPosition;
 			Carousel.ScrollTo(_initialPosition, position: Xamarin.Forms.ScrollToPosition.Center);
 			_isUpdatingPositionFromForms = false;
 		}

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

@@ -13,7 +13,7 @@ namespace Xamarin.Forms.Platform.Android
 	{
 		protected readonly TItemsView ItemsView;
 		readonly Func<View, Context, ItemContentView> _createItemContentView;
-		internal readonly TItemsViewSource ItemsSource;
+		internal TItemsViewSource ItemsSource;
 
 		bool _disposed;
 		Size? _size;
@@ -49,7 +49,11 @@ namespace Xamarin.Forms.Platform.Android
 
 		protected virtual void ItemsViewPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs property)
 		{
-			if (property.Is(Xamarin.Forms.ItemsView.HeaderProperty))
+			if (property.Is(Xamarin.Forms.ItemsView.ItemsSourceProperty))
+			{
+				UpdateItemsSource();
+			}
+			else if (property.Is(Xamarin.Forms.ItemsView.HeaderProperty))
 			{
 				UpdateHasHeader();
 			}
@@ -126,7 +130,8 @@ namespace Xamarin.Forms.Platform.Android
 				return new TextViewHolder(view);
 			}
 
-			var itemContentView = new ItemContentView(context);
+			var itemContentView = _createItemContentView.Invoke(ItemsView, context);
+
 			return new TemplatedItemViewHolder(itemContentView, ItemsView.ItemTemplate);
 		}
 
@@ -186,6 +191,13 @@ namespace Xamarin.Forms.Platform.Android
 			}
 		}
 
+		void UpdateItemsSource()
+		{
+			ItemsSource?.Dispose();
+
+			ItemsSource = CreateItemsSource();
+		}
+
 		void SetStaticSize(Size size)
 		{
 			_size = size;

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

@@ -7,10 +7,10 @@ namespace Xamarin.Forms.Platform.Android
 {
 	internal class SpacingItemDecoration : RecyclerView.ItemDecoration
 	{
-		ItemsLayoutOrientation _orientation;
-		double _verticalSpacing;
+		readonly ItemsLayoutOrientation _orientation;
+		readonly double _verticalSpacing;
 		double _adjustedVerticalSpacing = -1;
-		double _horizontalSpacing;
+		readonly double _horizontalSpacing;
 		double _adjustedHorizontalSpacing = -1;
 
 		public SpacingItemDecoration(IItemsLayout itemsLayout)
@@ -30,13 +30,9 @@ namespace Xamarin.Forms.Platform.Android
 				case ListItemsLayout listItemsLayout:
 					_orientation = listItemsLayout.Orientation;
 					if (_orientation == ItemsLayoutOrientation.Horizontal)
-					{
 						_horizontalSpacing = listItemsLayout.ItemSpacing;
-					}
 					else
-					{
 						_verticalSpacing = listItemsLayout.ItemSpacing;
-					}
 					break;
 			}
 		}

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

@@ -32,7 +32,7 @@ namespace Xamarin.Forms.Platform.iOS
 			var aspectRatio = size.Width / size.Height;
 			var numberOfVisibleItems = _carouselView.NumberOfSideItems * 2 + 1;
 			var width = (size.Width - _carouselView.PeekAreaInsets.Left - _carouselView.PeekAreaInsets.Right) / numberOfVisibleItems;
-			var height = size.Height / numberOfVisibleItems;
+			var height = (size.Height - _carouselView.PeekAreaInsets.Top - _carouselView.PeekAreaInsets.Bottom) / numberOfVisibleItems;
 
 			if (ScrollDirection == UICollectionViewScrollDirection.Horizontal)
 			{

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

@@ -1,5 +1,4 @@
-using System;
-using System.ComponentModel;
+using System.ComponentModel;
 
 namespace Xamarin.Forms.Platform.iOS
 {