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using System;
using Xamarin.Forms.Platform;
namespace Xamarin.Forms
{
[RenderWith(typeof(_CarouselViewRenderer))]
public class CarouselView : ItemsView, ICarouselViewController
{
public static readonly BindableProperty PositionProperty =
BindableProperty.Create(
propertyName: nameof(Position),
returnType: typeof(int),
declaringType: typeof(CarouselView),
defaultValue: 0,
defaultBindingMode: BindingMode.TwoWay
);
public static readonly BindableProperty ItemProperty =
BindableProperty.Create(
propertyName: nameof(Item),
returnType: typeof(object),
declaringType: typeof(CarouselView),
defaultValue: null,
defaultBindingMode: BindingMode.TwoWay
);
object _lastItem;
int _lastPosition;
public CarouselView()
{
_lastPosition = 0;
_lastItem = null;
VerticalOptions = LayoutOptions.FillAndExpand;
HorizontalOptions = LayoutOptions.FillAndExpand;
}
object GetItem(int position)
{
var controller = (IItemViewController)this;
object item = controller.GetItem(position);
return item;
}
// non-public bc unable to implement on iOS
internal event EventHandler<ItemVisibilityEventArgs> ItemAppearing;
internal event EventHandler<ItemVisibilityEventArgs> ItemDisappearing;
public int Position
{
get
{
return (int)GetValue(PositionProperty);
}
set
{
SetValue(PositionProperty, value);
}
}
public object Item
{
get
{
return GetValue(ItemProperty);
}
internal set
{
SetValue(ItemProperty, value);
}
}
public event EventHandler<SelectedItemChangedEventArgs> ItemSelected;
public event EventHandler<SelectedPositionChangedEventArgs> PositionSelected;
protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
{
var minimumSize = new Size(40, 40);
return new SizeRequest(minimumSize, minimumSize);
}
void ICarouselViewController.SendPositionAppearing(int position)
{
ItemAppearing?.Invoke(this, new ItemVisibilityEventArgs(GetItem(position)));
}
void ICarouselViewController.SendPositionDisappearing(int position)
{
ItemDisappearing?.Invoke(this, new ItemVisibilityEventArgs(GetItem(position)));
}
void ICarouselViewController.SendSelectedItemChanged(object item)
{
if (item.Equals(_lastItem))
return;
_lastItem = item;
Item = item;
ItemSelected?.Invoke(this, new SelectedItemChangedEventArgs(item));
}
void ICarouselViewController.SendSelectedPositionChanged(int position)
{
if (_lastPosition == position)
return;
_lastPosition = position;
Item = ((IItemViewController)this).GetItem(position);
PositionSelected?.Invoke(this, new SelectedPositionChangedEventArgs(position));
}
}
}
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