当用户在具有触摸功能的屏幕上从ScrollViewer中抬起手指时，会触发什么事件

我发现，当我点击ScrollViewer时，PointerPressed和PointerExited事件会按预期触发。但是，如果我在触摸屏幕并抬起手指后向任何方向滚动，除了PointerCaptureLost之外，不会触发任何事件，它在我滚动后立即提前触发。

当我捕获指针ID并用计时器轮询PointerPoint的状态时，即使在滚动后抬起手指，IsInContact标志也会保持为真。当我简单地点击屏幕时，它会像预期的那样工作。

ManipulationCompleted具有与上面相同的效果，并且我不能使用ViewChanged事件，因为它在我抬起手指之前就会触发。

这是一个bug还是我遗漏了什么？有没有其他方法可以检测用户何时将手指从屏幕上移开？这真让我抓狂。

下面的示例代码。你需要在触摸模式下使用模拟器，或者有一个可触摸的屏幕来测试：

代码：

using System;
using Windows.UI.Input;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
namespace App1
{
    public sealed partial class MainPage : Page
    {
        private readonly DispatcherTimer pointerTimer = new DispatcherTimer();
        private uint? CurrentPointerID; //container for the current pointer id when user makes contact with the screeen
        public MainPage()
        {
            this.InitializeComponent();
            scrollviewer.PointerPressed += scrollviewer_PointerPressed;
            scrollviewer.PointerMoved += scrollviewer_PointerMoved;
            scrollviewer.PointerExited += scrollviewer_PointerExited;
            scrollviewer.PointerReleased += scrollviewer_PointerReleased;
            scrollviewer.PointerCaptureLost += scrollviewer_PointerCaptureLost;
            scrollviewer.PointerCanceled += scrollviewer_PointerCanceled;

            pointerTimer.Tick += pointerTimer_Tick;
            pointerTimer.Interval = TimeSpan.FromMilliseconds(300);
            pointerTimer.Start();

        }
        #region ScrollViewer Events
        void scrollviewer_PointerMoved(object sender, PointerRoutedEventArgs e)
        {
            EventCalledTextBlock.Text = "Pointer Moved";
        }
        void scrollviewer_PointerExited(object sender, PointerRoutedEventArgs e)
        {
            EventCalledTextBlock.Text = "Pointer Exited";
        }
        void scrollviewer_PointerPressed(object sender, PointerRoutedEventArgs e)
        {
            CurrentPointerID = e.Pointer.PointerId;
            EventCalledTextBlock.Text = "Pointer Pressed";
        }
        void scrollviewer_PointerCanceled(object sender, PointerRoutedEventArgs e)
        {
            EventCalledTextBlock.Text = "Pointer Canceled";
        }
        void scrollviewer_PointerCaptureLost(object sender, PointerRoutedEventArgs e)
        {
            EventCalledTextBlock.Text = "Capture Lost";
        }
        void scrollviewer_PointerReleased(object sender, PointerRoutedEventArgs e)
        {
            EventCalledTextBlock.Text = "Pointer Released";
        }
        #endregion

        void pointerTimer_Tick(object sender, object e)
        {
            if (!CurrentPointerID.HasValue)
            {
                PollingTextBlock.Text = string.Empty;
                return;
            }
            try
            {
                var pointerPoint = PointerPoint.GetCurrentPoint(CurrentPointerID.Value);
                PollingTextBlock.Text = pointerPoint.IsInContact ? "Is In Contact" : "Not in Contact";
            }
            catch (Exception ex)
            {
                //This exception is raised when the user lifts finger without dragging.
                //assume finger is not in contact with screen
                PollingTextBlock.Text = "Not in Contact";
            }
        }
    }
}

XAML:

 <Page
    x:Class="App1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App1"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" Name="grid">
        <Grid.RowDefinitions>
            <RowDefinition Height="113*"/>
            <RowDefinition Height="655*"/>
        </Grid.RowDefinitions>
        <ScrollViewer x:Name="scrollviewer" VerticalScrollBarVisibility="Disabled" HorizontalScrollBarVisibility="Visible" Grid.Row="1" >
            <Rectangle Fill="#FF3783CF" Height="100" Stroke="#FF33D851" Width="{Binding ElementName=grid, Path=ActualWidth}" Margin="100" StrokeThickness="4" />
        </ScrollViewer>
        <StackPanel Orientation="Vertical" Margin="45,25,0,0">
            <StackPanel Orientation="Horizontal">
            <TextBlock  HorizontalAlignment="Left" TextWrapping="Wrap" Text="Event Called:" VerticalAlignment="Top" FontSize="24" Margin="0,0,20,0"/>
            <TextBlock x:Name="EventCalledTextBlock" HorizontalAlignment="Left" TextWrapping="Wrap" VerticalAlignment="Top" FontSize="24"/>
        </StackPanel>
        <StackPanel Orientation="Horizontal">
            <TextBlock  HorizontalAlignment="Left" TextWrapping="Wrap" Text="Polling Value:" VerticalAlignment="Top" FontSize="24" Margin="0,0,20,0"/>
            <TextBlock x:Name="PollingTextBlock" HorizontalAlignment="Left" TextWrapping="Wrap" VerticalAlignment="Top" FontSize="24"/>
        </StackPanel>
    </StackPanel>
    </Grid>
</Page>