[Android] ItemsUpdatingScrollMode in CarouselView

Author: kubaflo

src/Controls/src/Core/Handlers/Items/Android/MauiCarouselRecyclerView.cs

@@ -303,6 +303,9 @@ void CollectionItemsSourceChanged(object sender, System.Collections.Specialized.
 							UpdatePosition(carouselPosition);
 						}
 
+						UpdateAdapter();
+						ScrollToPosition(carouselPosition);
+
 						//If we are adding or removing the last item we need to update
 						//the inset that we give to items so they are centered
 						if (e.NewStartingIndex == count - 1 || removingLastElement)

src/Controls/tests/TestCases.HostApp/Issues/Issue29415.xaml

@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:local="clr-namespace:Maui.Controls.Sample"
+             x:Class="Maui.Controls.Sample.Issues.Issue29415">
+    <Grid Padding="10"
+          RowDefinitions="Auto,*,*">
+        <VerticalStackLayout
+            Grid.Row="0"
+            Padding="10">
+            <HorizontalStackLayout Spacing="10">
+                <RadioButton x:Name="ItemsUpdatingKeepItemsInView"
+                             Content="KeepItemsInView"
+                             FontSize="10"
+                             GroupName="ItemsUpdatingScrollModeGroup"
+                             CheckedChanged="OnItemsUpdatingScrollModeChanged"
+                             AutomationId="ItemsUpdatingKeepItemsInView"/>
+                <RadioButton x:Name="ItemsUpdatingKeepLastItemInView"
+                             Content="KeepLastItemInView"
+                             FontSize="10"
+                             GroupName="ItemsUpdatingScrollModeGroup"
+                             CheckedChanged="OnItemsUpdatingScrollModeChanged"
+                             AutomationId="ItemsUpdatingKeepLastItemInView"/>
+            </HorizontalStackLayout>
+            <HorizontalStackLayout Spacing="10"
+                                   Margin="0,5,0,0">
+                <RadioButton x:Name="ItemsUpdatingKeepScrollOffset"
+                             Content="KeepScrollOffset"
+                             FontSize="10"
+                             GroupName="ItemsUpdatingScrollModeGroup"
+                             CheckedChanged="OnItemsUpdatingScrollModeChanged"
+                             AutomationId="ItemsUpdatingKeepScrollOffset"/>
+                <Button Text="Add"
+                        Clicked="Button_Clicked"
+                        Command="{Binding AddItemCommand}"
+                        WidthRequest="120"
+                        AutomationId="AddButton"/>
+            </HorizontalStackLayout>
+        </VerticalStackLayout>
+        <local:CarouselView2 Grid.Row="1"
+                             x:Name="carouselView"
+                             HorizontalScrollBarVisibility="Never"
+                             IndicatorView="{x:Reference indicatorView}">
+            <local:CarouselView2.ItemTemplate>
+                <DataTemplate>
+                    <Border>
+                        <Label Text="{Binding .}"
+                               AutomationId="{Binding .}"
+                               HorizontalTextAlignment="Center"
+                               VerticalOptions="Center"/>
+                    </Border>
+                </DataTemplate>
+            </local:CarouselView2.ItemTemplate>
+        </local:CarouselView2>
+
+        <IndicatorView
+            x:Name="indicatorView"
+            Grid.Row="2"
+            HorizontalOptions="Center"
+            VerticalOptions="End"
+            Margin="0,0,0,20"
+            IndicatorColor="LightGray"
+            SelectedIndicatorColor="DarkGray"
+            IndicatorSize="12"/>
+    </Grid>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue29415.xaml.cs

@@ -0,0 +1,45 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 29415, "ItemsUpdatingScrollMode in CarouselView Not Working as expected", PlatformAffected.Android)]
+public partial class Issue29415 : ContentPage
+{
+	public ObservableCollection<string> Items { get; set; }
+	public Issue29415()
+	{
+		InitializeComponent();
+		Items = new ObservableCollection<string>
+		{
+			"Item1",
+			"Item2",
+		};
+		BindingContext = this;
+		carouselView.ItemsSource = Items;
+	}
+
+	private void OnItemsUpdatingScrollModeChanged(object sender, CheckedChangedEventArgs e)
+	{
+		if (e.Value && sender is RadioButton radioButton)
+		{
+
+			switch (radioButton.Content.ToString())
+			{
+				case "KeepItemsInView":
+					carouselView.ItemsUpdatingScrollMode = ItemsUpdatingScrollMode.KeepItemsInView;
+					break;
+				case "KeepLastItemInView":
+					carouselView.ItemsUpdatingScrollMode = ItemsUpdatingScrollMode.KeepLastItemInView;
+					break;
+				case "KeepScrollOffset":
+					carouselView.ItemsUpdatingScrollMode = ItemsUpdatingScrollMode.KeepScrollOffset;
+					break;
+			}
+		}
+	}
+
+	private void Button_Clicked(object sender, EventArgs e)
+	{
+		Items.Add($"Item{Items.Count + 1}");
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29415.cs

@@ -0,0 +1,37 @@
+// On iOS this test fails with CollectionView, but passes with CollectionView2, so only run it with CollectionView2
+#if TEST_FAILS_ON_WINDOWS // Carousel view tests fail on Windows
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue29415 : _IssuesUITest
+{
+	public Issue29415(TestDevice testDevice) : base(testDevice) { }
+
+	public override string Issue => "ItemsUpdatingScrollMode in CarouselView Not Working as expected";
+
+	[Test]
+	[Category(UITestCategories.CarouselView)]
+	public void ItemsUpdatingScrollModeShouldWork()
+	{
+		App.WaitForElement("ItemsUpdatingKeepItemsInView");
+		App.Tap("AddButton");
+		App.Tap("ItemsUpdatingKeepItemsInView");
+		App.WaitForElement("Item1");
+		App.Tap("ItemsUpdatingKeepLastItemInView");
+		App.Tap("AddButton");
+		App.WaitForElement("Item4");
+		App.Tap("ItemsUpdatingKeepLastItemInView");
+		App.Tap("AddButton");
+		App.WaitForElement("Item5");
+		App.Tap("ItemsUpdatingKeepScrollOffset");
+		App.Tap("AddButton");
+		App.WaitForElement("Item5");
+		App.Tap("ItemsUpdatingKeepItemsInView");
+		App.Tap("AddButton");
+		App.WaitForElement("Item1");
+	}
+}
+#endif