FFImageLoading advanced useage

[Wenfengcheng]

If you use CachedImage views inside ViewCells used by ListViews with ListViewCachingStrategy.RecycleElement enabled, don't rely on bindings for setting the Source property (they are so slow!) - please use ViewCell's OnBindingContextChanged override of a ViewCell implementation to update it, avoiding loading images to wrong views. Example:

public class MyCustomCell : ViewCell
{
	readonly CachedImage cachedImage = null;

	public MyCustomCell()
	{
		cachedImage = new CachedImage();
		View = cachedImage;
	}

	protected override void OnBindingContextChanged()
	{
		// you can also put cachedImage.Source = null; here to prevent showing old images occasionally
		cachedImage.Source = null;
		var item = BindingContext as Item;

		if (item == null)
		{
			return;
		}

		cachedImage.Source = item.ImageUrl;

		base.OnBindingContextChanged();
	}
}

https://github.com/luberda-molinet/FFImageLoading/wiki/Xamarin.Forms-Advanced
https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/listview/performance#RecycleElement