CarouselLayout.cs

public class CarouselLayout : ScrollView
{
	public enum IndicatorStyleEnum
	{
		None,
		Dots,
		Tabs
	}

	readonly StackLayout _stack;

	int _selectedIndex;

	public CarouselLayout ()
	{
		Orientation = ScrollOrientation.Horizontal;

		_stack = new StackLayout {
			Orientation = StackOrientation.Horizontal,
			Spacing = 0
		};

		Content = _stack;
	}

	public IndicatorStyleEnum IndicatorStyle { get; set; }

	public IList<View> Children {
		get {
			return _stack.Children;
		}
	}

	private bool _layingOutChildren;
	protected override void LayoutChildren (double x, double y, double width, double height)
	{
		base.LayoutChildren (x, y, width, height);
		if (_layingOutChildren) return;

		_layingOutChildren = true;
		foreach (var child in Children) child.WidthRequest = width;
		_layingOutChildren = false;
	}

	public static readonly BindableProperty SelectedIndexProperty =
		BindableProperty.Create(
			nameof(SelectedIndex), 
			typeof(int), 
			typeof(CarouselLayout), 
			0, 
			BindingMode.TwoWay,
			propertyChanged: async (bindable, oldValue, newValue) =>
			{
				await ((CarouselLayout)bindable).UpdateSelectedItem();
			}
		);

	public int SelectedIndex {
		get {
			return (int)GetValue (SelectedIndexProperty);
		}
		set {
			SetValue (SelectedIndexProperty, value);
		}
	}

	async Task UpdateSelectedItem ()
	{
		await Task.Delay(300);
		SelectedItem = SelectedIndex > -1 ? Children[SelectedIndex].BindingContext : null;
	}

	public static readonly BindableProperty ItemsSourceProperty =
		BindableProperty.Create(
			nameof(ItemsSource),
			typeof(IList),
			typeof(CarouselLayout),
			null,
			propertyChanging: (bindableObject, oldValue, newValue) =>
			{
				((CarouselLayout)bindableObject).ItemsSourceChanging();
			},
			propertyChanged: (bindableObject, oldValue, newValue) =>
			{
				((CarouselLayout)bindableObject).ItemsSourceChanged();
			}
		);

	public IList ItemsSource {
		get {
			return (IList)GetValue (ItemsSourceProperty);
		}
		set {
			SetValue (ItemsSourceProperty, value);
		}
	}

	void ItemsSourceChanging ()
	{
		if (ItemsSource == null) return;
		_selectedIndex = ItemsSource.IndexOf (SelectedItem);
	}

	void ItemsSourceChanged ()
	{
		_stack.Children.Clear ();
		foreach (var item in ItemsSource) {
			var view = (View)ItemTemplate.CreateContent ();
			var bindableObject = view as BindableObject;
			if (bindableObject != null)
				bindableObject.BindingContext = item;
			_stack.Children.Add (view);
		}

		if (_selectedIndex >= 0) SelectedIndex = _selectedIndex;
	}

	public DataTemplate ItemTemplate {
		get;
		set;
	}

	public static readonly BindableProperty SelectedItemProperty =
		BindableProperty.Create(
			nameof(SelectedItem),
			typeof(object),
			typeof(CarouselLayout),
			null,
			BindingMode.TwoWay,
			propertyChanged: (bindable, oldValue, newValue) =>
			{
				((CarouselLayout)bindable).UpdateSelectedIndex();
			}
		);

	public object SelectedItem {
		get {
			return GetValue (SelectedItemProperty);
		}
		set {
			SetValue (SelectedItemProperty, value);
		}
	}

	void UpdateSelectedIndex ()
	{
		if (SelectedItem == BindingContext) return;

		SelectedIndex = Children
			.Select (c => c.BindingContext)
			.ToList ()
			.IndexOf (SelectedItem);
	}
}