Add sample page for ListIsNullOrEmptyConvertor (#780)

* Add sample page for ListIsNullOrEmptyConvertor

* Remove HasUnevenRows

Co-authored-by: Andrei <[email protected]>
Co-authored-by: Pedro Jesus <[email protected]>
Co-authored-by: Gerald Versluis <[email protected]>

Author: 4 people

samples/XCT.Sample/Pages/Converters/ListIsNullOrEmptyPage.xaml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<pages:BasePage xmlns="http://xamarin.com/schemas/2014/forms"
+                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+                xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
+                xmlns:pages="clr-namespace:Xamarin.CommunityToolkit.Sample.Pages"
+                xmlns:vm="clr-namespace:Xamarin.CommunityToolkit.Sample.ViewModels.Converters"
+                x:Class="Xamarin.CommunityToolkit.Sample.Pages.Converters.ListIsNullOrEmptyPage">
+
+    <pages:BasePage.BindingContext>
+        <vm:ListIsNullOrEmptyViewModel />
+    </pages:BasePage.BindingContext>
+
+    <AbsoluteLayout>
+        <ListView ItemsSource="{Binding Items}"
+                  IsVisible="{Binding Items, Converter={xct:ListIsNotNullOrEmptyConverter}}">
+            <ListView.ItemTemplate>
+                <DataTemplate>
+                    <ViewCell>
+                        <Label Text="{Binding Name}" />
+                    </ViewCell>
+                </DataTemplate>
+            </ListView.ItemTemplate>
+        </ListView>
+        <Label Text="Collection is empty" 
+               AbsoluteLayout.LayoutBounds="0,0,1,1" 
+               AbsoluteLayout.LayoutFlags="All"
+               IsVisible="{Binding Items, Converter={xct:ListIsNullOrEmptyConverter}}" 
+               VerticalOptions="CenterAndExpand" 
+               HorizontalOptions="CenterAndExpand"
+               HorizontalTextAlignment="Center" />
+
+        <StackLayout Orientation="Horizontal" Margin="5" Spacing="5"
+                     AbsoluteLayout.LayoutFlags="PositionProportional"
+                     AbsoluteLayout.LayoutBounds="1,1,AutoSize,AutoSize">
+            <Button Text="Add" Command="{Binding AddItemCommand}" />
+            <Button Text="Remove" Command="{Binding RemoveItemCommand}" IsEnabled="{Binding Items, Converter={xct:ListIsNotNullOrEmptyConverter}}" />
+        </StackLayout>
+    </AbsoluteLayout>
+</pages:BasePage>

samples/XCT.Sample/Pages/Converters/ListIsNullOrEmptyPage.xaml.cs

@@ -0,0 +1,8 @@
+namespace Xamarin.CommunityToolkit.Sample.Pages.Converters
+{
+	public partial class ListIsNullOrEmptyPage : BasePage
+	{
+		public ListIsNullOrEmptyPage()
+			=> InitializeComponent();
+	}
+}

samples/XCT.Sample/ViewModels/Converters/ConvertersGalleryViewModel.cs

@@ -40,6 +40,11 @@ public class ConvertersGalleryViewModel : BaseGalleryViewModel
 				typeof(VariableMultiValueConverterPage),
 				nameof(VariableMultiValueConverter),
 				"A converter that allows you to combine multiple boolean bindings into a single binding."),
+
+			new SectionModel(
+				typeof(ListIsNullOrEmptyPage),
+				nameof(ListIsNullOrEmptyConverter),
+				"A converter that allows you to check if collection is null or empty"),
 		};
 	}
 }

samples/XCT.Sample/ViewModels/Converters/ListIsNullOrEmptyViewModel.cs

@@ -0,0 +1,30 @@
+using Xamarin.CommunityToolkit.ObjectModel;
+using Xamarin.Forms;
+
+namespace Xamarin.CommunityToolkit.Sample.ViewModels.Converters
+{
+	public class ListIsNullOrEmptyViewModel : BaseViewModel
+	{
+		public ObservableRangeCollection<Person> Items { get; } = new ObservableRangeCollection<Person>();
+
+		public ListIsNullOrEmptyViewModel()
+		{
+			AddItemCommand = new Command(() =>
+			{
+				Items.Add(new Person
+				{
+					Id = Items.Count,
+					Name = $"Person {Items.Count}"
+				});
+			});
+			RemoveItemCommand = new Command(() => Items.RemoveAt(0));
+
+			// ListIsNullOrEmptyConvertor needs to know that Items are updated
+			Items.CollectionChanged += (sender, e) => OnPropertyChanged(nameof(Items));
+		}
+
+		public Command AddItemCommand { get; }
+
+		public Command RemoveItemCommand { get; }
+	}
+}