【发布时间】：2013-12-13 02:28:59
【问题描述】：
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，它会在我滚动时立即触发。
当我捕获指针 ID 并使用计时器轮询 PointerPoint 的状态时，IsInContact 标志保持为真，即使在我滚动后抬起手指也是如此。当我只需点击屏幕时，它就会按预期工作。
ManipulationCompleted 与上面的效果相同，我不能使用 ViewChanged 事件，因为它在我抬起手指之前触发。
这是一个错误还是我在这里遗漏了什么？是否有另一种方法可以检测用户何时将手指从屏幕上抬起？这让我很生气。
下面的示例代码。您需要在触摸模式下使用模拟器或使用可触摸的屏幕进行测试：
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>
【问题讨论】：
-
你尝试过操纵事件而不是指针事件吗？
-
是的。它会导致与上述相同的行为，即在滚动后永远不会调用 ManipulationCompleted。
-
我想知道您的 ScrollViewer 中的 Rectangle 是否正在“吃掉”您的 Pointer Released 事件。
-
理论不错，但是当我通过 ((UIElement) scrollviewer.Content) 将指针事件添加到 Rectangle 时，它们根本不会触发。同样在 Rectangle 上设置 ManipulationMode 允许引发 Scrollviewer 上的 PointerExit 事件，但是这会一起禁用滚动。
-
嗯，我记得在 MSDN 文档中读到 PointerReleased 事件并不总是必须触发。它给出了为什么会出现这种情况的几个原因。找到了。请查看“不要依赖总是成对发生的 PointerPressed 和 PointerReleased 事件。要正常运行，您的应用程序必须侦听并处理所有代表 Press 操作可能得出的结论的事件。”这是链接：msdn.microsoft.com/library/windows/apps/br208972
标签： c# xaml windows-runtime windows-store-apps winrt-xaml