[C#/WINUI3/.NET8] ScrollViewer 클래스 : CurrentAnchor 속성을 사용해 ItemsRepeater 객체에서 현재 앵커 항목을 구하기

■ ScrollViewer 클래스의 CurrentAnchor 속성을 사용해 ItemsRepeater 객체에서 현재 앵커 항목을 구하는 방법을 보여준다.

※ 비주얼 스튜디오에서 TestProject(Unpackaged) 모드로 빌드한다.
※ TestProject.csproj 프로젝트 파일에서 WindowsPackageType 태그를 None으로 추가했다.

▶ MainPage.xaml


<?xml version="1.0" encoding="utf-8"?>
<Page x:Class="TestProject.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
    FontFamily="나눔고딕코딩"
    FontSize="16">
    <Grid Margin="10">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"    />
            <RowDefinition Height="10"   />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <Border Grid.Row="0"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            BorderThickness="1"
            BorderBrush="DarkGray">
            <ScrollViewer Name="scrollViewer">
                <ItemsRepeater Name="itemsRepeater">
                    <ItemsRepeater.ItemTemplate>
                        <DataTemplate x:DataType="x:String">
                            <TextBlock
                                Margin="5"
                                Text="{x:Bind}" />
                        </DataTemplate>
                    </ItemsRepeater.ItemTemplate>
                </ItemsRepeater>
            </ScrollViewer>
        </Border>
        <TextBlock Name="messageTextBlock" Grid.Row="2"
            HorizontalAlignment="Stretch"
            Padding="5" />
    </Grid>
</Page>

<?xml version="1.0" encoding="utf-8"?>

<Page x:Class="TestProject.MainPage"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"

FontFamily="나눔고딕코딩"

FontSize="16">

<Grid.RowDefinitions>

</Grid.RowDefinitions>

<Border Grid.Row="0"

HorizontalAlignment="Center"

VerticalAlignment="Center"

BorderThickness="1"

BorderBrush="DarkGray">

<ItemsRepeater.ItemTemplate>

<TextBlock

Margin="5"

Text="{x:Bind}" />

</DataTemplate>

</ItemsRepeater.ItemTemplate>

</ItemsRepeater>

</ScrollViewer>

</Border>

<TextBlock Name="messageTextBlock" Grid.Row="2"

HorizontalAlignment="Stretch"

Padding="5" />

</Grid>

</Page>

▶ MainPage.xaml.cs


using System.Collections.ObjectModel;

using Windows.Foundation;

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;

namespace TestProject;

/// <summary>
/// 메인 페이지
/// </summary>
public sealed partial class MainPage : Page
{
    //////////////////////////////////////////////////////////////////////////////////////////////////// Constructor
    ////////////////////////////////////////////////////////////////////////////////////////// Public

    #region 생성자 - MainPage()

    /// <summary>
    /// 생성자
    /// </summary>
    public MainPage()
    {
        InitializeComponent();

        ObservableCollection<string> collection = new ObservableCollection<string>();

        for(int i = 1; i < 100; i++)
        {
            collection.Add($"항목 {i}");
        }

        this.itemsRepeater.ItemsSource = collection;

        this.scrollViewer.ViewChanged += scrollViewer_ViewChanged;
    }

    #endregion

    //////////////////////////////////////////////////////////////////////////////////////////////////// Method
    ////////////////////////////////////////////////////////////////////////////////////////// Public

    #region 스크롤 뷰어 뷰 변경시 처리하기 - scrollViewer_ViewChanged(sender, e)

    /// <summary>
    /// 스크롤 뷰어 뷰 변경시 처리하기
    /// </summary>
    /// <param name="sender">이벤트 발생자</param>
    /// <param name="e">이벤트 인자</param>
    private void scrollViewer_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)
    {
        UIElement anchorElement = this.scrollViewer.CurrentAnchor;

        if(anchorElement == null)
        {
            this.messageTextBlock.Text = string.Empty;

            return;
        }

        string itemText = (anchorElement as TextBlock).Text;

        Rect anchorRectangle = anchorElement.TransformToVisual(this.scrollViewer).TransformBounds(new Rect(0, 0, anchorElement.ActualSize.X, anchorElement.ActualSize.Y));

        double anchorRelativeVerticalOffset = this.scrollViewer.VerticalOffset - anchorRectangle.Top;

        this.messageTextBlock.Text = $"앵커 항목 : {itemText} : 앵커 상대적 오프셋 : {anchorRelativeVerticalOffset:0.00} : 스크롤 뷰어 오프셋 : {this.scrollViewer.VerticalOffset:0.00}";
    }

    #endregion
}

using System.Collections.ObjectModel;

using Windows.Foundation;

using Microsoft.UI.Xaml;

using Microsoft.UI.Xaml.Controls;

namespace TestProject;

/// <summary>

/// 메인 페이지

/// </summary>

public sealed partial class MainPage : Page

{

//////////////////////////////////////////////////////////////////////////////////////////////////// Constructor

////////////////////////////////////////////////////////////////////////////////////////// Public

#region 생성자 - MainPage()

/// <summary>

/// 생성자

/// </summary>

public MainPage()

{

InitializeComponent();

ObservableCollection<string> collection = new ObservableCollection<string>();

for(int i = 1; i < 100; i++)

{

collection.Add($"항목 {i}");

}

this.itemsRepeater.ItemsSource = collection;

this.scrollViewer.ViewChanged += scrollViewer_ViewChanged;

}

#endregion

//////////////////////////////////////////////////////////////////////////////////////////////////// Method

////////////////////////////////////////////////////////////////////////////////////////// Public

#region 스크롤 뷰어 뷰 변경시 처리하기 - scrollViewer_ViewChanged(sender, e)

/// <summary>

/// 스크롤 뷰어 뷰 변경시 처리하기

/// </summary>

/// <param name="sender">이벤트 발생자</param>

/// <param name="e">이벤트 인자</param>

private void scrollViewer_ViewChanged(object sender, ScrollViewerViewChangedEventArgs e)

{

UIElement anchorElement = this.scrollViewer.CurrentAnchor;

if(anchorElement == null)

{

this.messageTextBlock.Text = string.Empty;

return;

}

string itemText = (anchorElement as TextBlock).Text;

Rect anchorRectangle = anchorElement.TransformToVisual(this.scrollViewer).TransformBounds(new Rect(0, 0, anchorElement.ActualSize.X, anchorElement.ActualSize.Y));

double anchorRelativeVerticalOffset = this.scrollViewer.VerticalOffset - anchorRectangle.Top;

this.messageTextBlock.Text = $"앵커 항목 : {itemText} : 앵커 상대적 오프셋 : {anchorRelativeVerticalOffset:0.00} : 스크롤 뷰어 오프셋 : {this.scrollViewer.VerticalOffset:0.00}";

}

#endregion

}

TestProject.zip