maui-linux/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue3008.cs

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

#if UITEST
using Xamarin.UITest;
using NUnit.Framework;
using Xamarin.Forms.Core.UITests;
#endif

namespace Xamarin.Forms.Controls.Issues
{
	[Preserve(AllMembers = true)]
	[Issue(IssueTracker.Github, 3008, "Setting ListView.ItemSource to null doesn't cause it clear out its contents", PlatformAffected.UWP)]
#if UITEST
	[NUnit.Framework.Category(UITestCategories.ListView)]
#endif
	public class Issue3008 : TestContentPage
	{
		ListView _listView;
		ListView _listViewIsGrouped;
		const string success1 = "InitialLoad: you should see a grouped and not grouped list view";
		const string successEmpty1 = "Source is set to null: you should see nothing";
		const string success2 = "Reload1: you should see a grouped and not grouped list view";
		const string successEmpty2 = "If you see nothing now test has passed";
		const string successEmpty3 = "List loaded and ItemSource not set: you should see nothing";


		[Preserve(AllMembers = true)]
		class MyHeaderViewCell : ViewCell
		{
			public MyHeaderViewCell()
			{
				Height = 25;
				var label = new Label { VerticalOptions = LayoutOptions.Center };
				label.SetBinding(Label.TextProperty, nameof(GroupedItem.Name));
				View = label;
			}
		}

		[Preserve(AllMembers = true)]
		class GroupedItem : List<Item>
		{
			public GroupedItem()
			{
				AddRange(Enumerable.Range(0, 3).Select(i => new Item()));
			}
			public string Name { get; set; }
		}


		[Preserve(AllMembers = true)]
		class Item
		{

		}

		void LoadData()
		{
			_listViewIsGrouped.ItemsSource = new ObservableCollection<GroupedItem>(Enumerable.Range(0, 3).Select(x => new GroupedItem() { Name = $"Group {x}" }));
			_listView.ItemsSource = new ObservableCollection<Item>(Enumerable.Range(0, 13).Select(x => new Item()));

		}

		void ReloadListViews()
		{
			StackLayout content = Content as StackLayout;

			if (_listView != null)
			{
				content.Children.Remove(_listView);
				content.Children.Remove(_listViewIsGrouped);
			}
			_listView = new ListView
			{
				ItemTemplate = new DataTemplate(() =>
				{
					Label nameLabel = new Label() { Text = "Not Grouped Item" };
					var cell = new ViewCell
					{
						View = nameLabel,
					};
					return cell;
				}),
			};
			_listViewIsGrouped = new ListView
			{
				IsGroupingEnabled = true,
				GroupHeaderTemplate = new DataTemplate(typeof(MyHeaderViewCell)),
				ItemTemplate = new DataTemplate(() =>
				{
					Label nameLabel = new Label() { Text = "Grouped Item" };
					var cell = new ViewCell
					{
						View = nameLabel,
					};
					return cell;
				}),
			};

			content.Children.Add(_listView);
			content.Children.Add(_listViewIsGrouped);
		}

		protected override void Init()
		{
			Label label = new Label();

			int clickCount = 0;
			Content = new StackLayout
			{
				Children =
				{
					label,
					new Button()
					{
						Text = "Click Until Success",
						Command = new Command(() =>
						{
							if(clickCount == 0)
							{
								LoadData();
								label.Text = success1;
							}
							else if(clickCount == 1)
							{
								ReloadListViews();
								LoadData();
								label.Text = success1;
							}
							else if(clickCount <= 3)
							{
								if(_listViewIsGrouped.ItemsSource != null)
								{
									_listViewIsGrouped.ItemsSource = null;
									_listView.ItemsSource = null;
									label.Text = successEmpty1;
								}
								else
								{
									LoadData();
									label.Text = success2;
								}
							}
							else if(clickCount <= 5)
							{
								if(_listViewIsGrouped.ItemsSource != null)
								{
									ReloadListViews();
									label.Text = successEmpty3;
								}
								else
								{
									LoadData();
									label.Text = success2;
								}
							}
							else
							{
								if(_listViewIsGrouped.ItemsSource != null)
								{
									_listViewIsGrouped.ItemsSource = new List<GroupedItem>();
									_listView.ItemsSource = new List<Item>();
									label.Text = successEmpty2;
								}
							}

							clickCount++;
						})
					}
				},
			};

			ReloadListViews();
		}

#if UITEST && !__ANDROID__
		[Test]
		public void EnsureListViewEmptiesOut()
		{
			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForElement("Not Grouped Item");
			RunningApp.WaitForElement("Grouped Item");

			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForElement("Not Grouped Item");
			RunningApp.WaitForElement("Grouped Item");

			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForNoElement("Not Grouped Item");
			RunningApp.WaitForNoElement("Grouped Item");

			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForElement("Not Grouped Item");
			RunningApp.WaitForElement("Grouped Item");
		
			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForNoElement("Not Grouped Item");
			RunningApp.WaitForNoElement("Grouped Item");

			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForElement("Not Grouped Item");
			RunningApp.WaitForElement("Grouped Item");

			RunningApp.Tap("Click Until Success");
			RunningApp.WaitForNoElement("Not Grouped Item");
			RunningApp.WaitForNoElement("Grouped Item");
		}
#endif

	}
}