MVVM Light ObservableAdapter V0.0.1

namespace GalaSoft.MvvmLight.Helpers
{
	/// <summary>
	/// A <see cref="BaseAdapter{T}"/> that can be used with an Android ListView. After setting
	/// the <see cref="DataSource"/> and the <see cref="GetTemplate"/> properties, the adapter is
	/// suitable for a list control. If the DataSource is an <see cref="INotifyCollectionChanged"/>,
	/// changes to the collection will be observed and the UI will automatically be updated.
	/// </summary>
	/// <typeparam name="T">The type of the items contained in the <see cref="DataSource"/>.</typeparam>
	////[ClassInfo(typeof(ObservableAdapter<T>),
	////    VersionString = "0.0.1",
	////    DateString = "201405262134",
	////    UrlContacts = "http://www.galasoft.ch/contact_en.html",
	////    Email = "[email protected]")]
	public class ObservableAdapter<T> : BaseAdapter<T>
	{
		private IList<T> _list;
		private INotifyCollectionChanged _notifier;

		/// <summary>
		/// Gets the number of items in the DataSource.
		/// </summary>
		public override int Count
		{
			get
			{
				return _list == null ? 0 : _list.Count;
			}
		}

		/// <summary>
		/// Gets or sets the list containing the items to be represented in the list control.
		/// </summary>
		public IList<T> DataSource
		{
			get
			{
				return _list;
			}
			set
			{
				if (_list == value)
				{
					return;
				}

				if (_notifier != null)
				{
					_notifier.CollectionChanged -= NotifierCollectionChanged;
				}

				_list = value;
				_notifier = _list as INotifyCollectionChanged;

				if (_notifier != null)
				{
					_notifier.CollectionChanged += NotifierCollectionChanged;
				}
			}
		}

		/// <summary>
		/// Gets and sets a method taking an item's position in the list, the item itself,
		/// and a recycled Android View, and returning an adapted View for this item. Note that the recycled
		/// view might be null, in which case a new View must be inflated by this method.
		/// </summary>
		public Func<int, T, View, View> GetTemplate
		{
			get;
			set;
		}

		/// <summary>
		/// Gets and sets a method that returns a unique ID for an item. If NULL the item's position is used.
		/// </summary>
		public Func<T, long> GetId {
			get;
			set;
		}

		/// <summary>
		/// Gets the item corresponding to the index in the DataSource.
		/// </summary>
		/// <param name="index">The index of the item that needs to be returned.</param>
		/// <returns>The item corresponding to the index in the DataSource</returns>
		public override T this[int index]
		{
			get
			{
				return _list == null ? default(T) : _list[index];
			}
		}

		/// <summary>
		/// Returns a unique ID for the item corresponding to the <see cref="position"/> parameter.
		/// In this implementation, the method always returns the position itself.
		/// </summary>
		/// <param name="position">The position of the item for which the ID needs to be returned.</param>
		/// <returns>A unique ID for the item corresponding to the <see cref="position"/> parameter.</returns>
		public override long GetItemId(int position)
		{
			if (this.GetId == null)
			{
				return position;
			}

			return this.GetId (this [position]);
		}

		/// <summary>
		/// Prepares the view (template) for the item corresponding to the <see cref="position"/>
		/// in the DataSource. This method calls the <see cref="GetTemplate"/> method so that the caller
		/// can create (if necessary) and adapt the template for the corresponding item.
		/// </summary>
		/// <param name="position">The position of the item in the DataSource.</param>
		/// <param name="convertView">A recycled view. If this parameter is null,
		/// a new view must be inflated.</param>
		/// <param name="parent">The view's parent.</param>
		/// <returns>A view adapted for the item at the corresponding position.</returns>
		public override View GetView(int position, View convertView, ViewGroup parent)
		{
			if (GetTemplate == null)
			{
				return convertView;
			}

			var item = _list[position];
			var view = GetTemplate(position, item, convertView);
			return view;
		}

		private void NotifierCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			NotifyDataSetChanged();
		}
	}
}