c# - 触摸滚动在 WPF 中不起作用

Question

我有一个 WPF 应用程序，其中一部分我有一张显示 Javascript 的卡片。我的问题是我无法用鼠标在 Javascript 卡片上滚动，因为它吞没了事件。我通过连接到 UIElement 发送的 PreviewMouseWheel 事件(此处描述)解决了这个问题:

protected void AddListeners(BorderedCanvas borderedCanvas)
{
    borderedCanvas.PreviewMouseWheel += PreviewMouseWheel;
}

protected void RemoveListeners(BorderedCanvas borderedCanvas)
{
    borderedCanvas.PreviewMouseWheel -= PreviewMouseWheel;
}

protected static void PreviewMouseWheel(object sender, MouseWheelEventArgs e)
{
    if (!e.Handled)
    {
        e.Handled = true;

        var eventArg =
            new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta)
            {
                RoutedEvent = UIElement.MouseWheelEvent,
                Source = sender
            };

        var parent = VisualTreeHelper.GetParent((UIElement)sender) as UIElement;
        parent?.RaiseEvent(eventArg);
    }
}

现在，使用鼠标滚动效果非常好。

但是，触摸滚动不起作用。

所以，我修改了AddListeners:

    protected void AddListeners(BorderedCanvas borderedCanvas)
    {
        borderedCanvas.PreviewMouseWheel += PreviewMouseWheel;
        borderedCanvas.PreviewTouchDown += new EventHandler<TouchEventArgs>(OnTouchDown);
        borderedCanvas.PreviewTouchMove += new EventHandler<TouchEventArgs>(OnTouchMove);
    }

我添加了这些方法:

    protected static void OnTouchDown(object sender, TouchEventArgs e)
    {
        if (!e.Handled)
        {
            e.Handled = true;

            var eventArg =
                new TouchEventArgs(e.TouchDevice, e.Timestamp)
                {
                    RoutedEvent = UIElement.TouchDownEvent,
                    Source = sender
                };

            var parent = VisualTreeHelper.GetParent((UIElement)sender) as UIElement;
            parent?.RaiseEvent(eventArg);
        }
    }

    protected static void OnTouchMove(object sender, TouchEventArgs e)
    {
        if (!e.Handled)
        {
            e.Handled = true;

            var eventArg =
                new TouchEventArgs(e.TouchDevice, e.Timestamp)
                {
                    RoutedEvent = UIElement.TouchMoveEvent,
                    Source = sender
                };

            var parent = VisualTreeHelper.GetParent((UIElement)sender) as UIElement;
            parent?.RaiseEvent(eventArg);
        }
    }

但是，触摸滚动仍然不起作用。

知道我做错了什么吗？

对我来说，我似乎以类似的方式处理鼠标滚动和触摸滚动，但第一个有效而第二个无效。

Answer 1

您需要设置 ScrollViewer.PanningMode 以使其与触摸一起工作。

<ScrollViewer PanningMode="Both"/>

PanningMode 的默认值为 None。