maui-linux/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla60524.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using Xamarin.Forms.Internals;
using Xamarin.Forms.CustomAttributes;

#if UITEST
using Xamarin.UITest;
using NUnit.Framework;
#endif

namespace Xamarin.Forms.Controls.Issues
{
	[Preserve(AllMembers = true)]
	[Issue(IssueTracker.Bugzilla, 60524, "NRE when rendering ListView with grouping enabled and HasUnevenRows set to true", PlatformAffected.iOS)]
	public class Bugzilla60524 : TestNavigationPage
	{
		[Preserve(AllMembers = true)]
		public class GroupedItemsPage : ContentPage
		{
			private ObservableCollection<Grouping<string, GroupedItem>> model;
			private ListView listView;

			public GroupedItemsPage()
			{
				listView = new ListView(ListViewCachingStrategy.RetainElement) { HasUnevenRows = true };
				listView.IsGroupingEnabled = true;
				listView.ItemTemplate = new GroupedItemsDataTemplateSelector();

				var headerCell = new DataTemplate(typeof(TextCell));
				headerCell.SetBinding(TextCell.TextProperty, "Key");
				this.listView.GroupHeaderTemplate = headerCell;

				this.model = new ObservableCollection<Grouping<string, GroupedItem>>();
				this.GetItems();

				this.SetMainContent();
			}

			private void GetItems()
			{
				var zeroGroup = new Grouping<string, GroupedItem>("Group 0", new List<GroupedItem> {
				});

				var firstGroup = new Grouping<string, GroupedItem>("Group 1", new List<GroupedItem> {
					new GroupedItem("Group 1", "Item 1"),
					new GroupedItem("Group 1", "Item 2")
				});

				var secondGroup = new Grouping<string, GroupedItem>("Group 2", new List<GroupedItem> {
					new GroupedItem("Group 2", "Item 3"),
					new GroupedItem("Group 2", "Item 4")
				});

				model.Add(zeroGroup);
				model.Add(firstGroup);
				model.Add(secondGroup);

				this.listView.ItemsSource = model;
			}

			private void SetMainContent()
			{
				var content = new StackLayout
				{
					VerticalOptions = LayoutOptions.FillAndExpand,
					Children = { new Label { Text = "If this page does not crash, this test has passed." }, this.listView }
				};

				Content = content;
			}
		}
		[Preserve(AllMembers = true)]
		public class GroupedItemsDataTemplateSelector : Xamarin.Forms.DataTemplateSelector
		{
			private readonly DataTemplate firstGroupTemplate;
			private readonly DataTemplate secondGroupTemplate;

			public GroupedItemsDataTemplateSelector()
			{
				// Retain instances
				var firstTemplate = new DataTemplate(typeof(TextCell));
				firstTemplate.SetBinding(TextCell.TextProperty, "Item");
				this.firstGroupTemplate = firstTemplate;

				var secondTemplate = new DataTemplate(typeof(ImageCell));
				secondTemplate.SetBinding(ImageCell.TextProperty, "Item");
				this.secondGroupTemplate = secondTemplate;
			}

			protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
			{
				var model = item as GroupedItem;

				if (model == null)
				{
					return null;
				}

				return model.Group == "Group 1" ? this.firstGroupTemplate : this.secondGroupTemplate;
			}
		}
		[Preserve(AllMembers = true)]
		public class GroupedItem
		{
			public string Group { get; set; }

			public string Item { get; set; }

			public GroupedItem(string group, string item)
			{
				this.Group = group;
				this.Item = item;
			}
		}
		[Preserve(AllMembers = true)]
		public class Grouping<K, T> : ObservableCollection<T>
		{
			public K Key { get; private set; }

			public IList<T> Values
			{
				get { return this.Items; }
			}

			public Grouping(K key, IEnumerable<T> items)
			{
				Key = key;
				foreach (var item in items)
				{
					this.Items.Add(item);
				}
			}

			public Grouping(IGrouping<K, T> grouping)
			{
				Key = grouping.Key;
				foreach (var item in grouping)
				{
					this.Items.Add(item);
				}
			}

			public void AddRange(IList<T> values)
			{
				foreach (var item in values)
				{
					this.Items.Add(item);
				}
			}
		}
		[Preserve(AllMembers = true)]
		public class GroupingKey
		{
			public string Title { get; private set; }

			public string Abbreviation { get; private set; }

			public GroupingKey(string Title, string abbrevation)
			{
				this.Title = Title;
				this.Abbreviation = abbrevation;
			}
		}

		protected override void Init()
		{
			Navigation.PushAsync(new GroupedItemsPage());
		}

#if UITEST
		[Test]
		public void Bugzilla60524Test()
		{
			RunningApp.WaitForElement(q => q.Marked("Group 1"));
		}
#endif
	}
}