我发现当我点击ScrollViewer时,将按预期触发PointerPressed和PointerExited事件。但是,如果在触摸屏幕并抬起手指后向任意方向滚动,则不会触发任何事件,只有PointerCaptureLost会在我滚动时过早触发。
当我捕获指针ID并使用计时器轮询PointerPoint的状态时,即使滚动后抬起手指,IsInContact标志仍为true。当我只需点击屏幕时,它就会按预期工作。
ManipulationCompleted具有与上述相同的效果,我无法使用ViewChanged事件,因为在我抬起手指之前会触发ViewChanged事件。
这是一个错误还是我在这里错过了一些东西?我还有其他方法可以检测到用户何时将手指抬离屏幕吗?这在驱赶我香蕉。
下面的示例代码。您需要以触摸模式使用模拟器或具有可触摸屏幕以测试:
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>
最佳答案
由于遇到了类似的问题,所以我偶然发现了这个问题。我有一个包含多个图像的ScrollViewer,我想知道ScrollViewer停止移动时显示的图像...
最后,我确实使用了ScrollViewer.ViewChanged事件。此事件一直触发直到滚动完成。
实际上,我只对这些事件中的最后一个感兴趣,但是由于没有事件仅在该特定时刻触发,因此我需要对此作出回应,并自己检查是否是采取行动的适当时机。
我希望这有帮助。
ScrollViewer.ViewChanged事件:https://msdn.microsoft.com/en-us/library/windows/apps/windows.ui.xaml.controls.scrollviewer.viewchanged?f=255&MSPPError=-2147217396