WPF拖动滚动无法正常工作 [英] WPF Drag-to-scroll doesn't work correctly

问题描述

我想要在我的应用程序中实现一个拖曳到滚动的功能，并在我的路上有问题。有谁能够帮助我？
我有一个ScrollViewer，里面有一个ItemsControl，在ItemsTemplate里面我有一个UserControl。我想在ItemsControl中拖动该UserControl。当我拖动到ItemsControl的边界时，我希望ScrollViewer向下滚动。

  protected override void OnPreviewMouseMove（System。 Windows.Input.MouseEventArgs e）
 {
 if（this.IsMouseCaptured）
 {
 //获取新的鼠标位置。 
点mouseDragCurrentPoint = e.GetPosition（this）; 
 
 if（Math.Abs​​（mouseDragCurrentPoint.Y  -  this.ActualHeight）< = 50）
 {
 this._scrollStartOffset.Y + = 5; 
 _containingScrollViewer.ScrollToVerticalOffset（this._scrollStartOffset.Y）; 
} 
 if（mouseDragCurrentPoint.Y< = 50）
 {
 this._scrollStartOffset.Y  -  = 5; 
 _containingScrollViewer.ScrollToVerticalOffset（this._scrollStartOffset.Y）; 
} 
} 
 base.OnPreviewMouseMove（e）; 
} 
  

当我开始拖动调用 DragDrop.DoDragDrop ）滚动不要发生。但是当我禁用拖动时，ScrollViewer会根据鼠标位置滚动。
也许有没有什么东西，我不会在accont关于拖动和捕获鼠标？
感谢关注。
Garegin

解决方案

当使用DragDrop.DoDragDrop（）时，我使用一个处理Me.DragOver事件的Sub在VB中），所以它看起来如下。记住你，我的控件有一个包含在ScrollViewer中的ListBox。

  Private Sub ListBox_Items_DragOver（ByVal sender As System.Object，ByVal e作为System.Windows.DragEventArgs）处理Me.DragOver 
 Dim currentMousePoint As Point = e.GetPosition（_containtingScrollViewer）
如果Math.Abs​​（currentMousePoint.Y  -  _containtingScrollViewer.ActualHeight）< = 50然后
 _containtingScrollViewer.ScrollToVerticalOffset（currentMousePoint.Y + 5）
 End If 
如果currentMousePoint.Y< = 50然后
 _containtingScrollViewer.ScrollToVerticalOffset（currentMousePoint.Y  -  5）
结束如果
 End Sub 
  

这使我能够在拖动项目时滚动。您可以根据需要调整公差以获得更好/更平滑的滚动。

I am tying to realize a drag-to-scroll functionality in my application and have problems on my way. Can anybody help me? I have a ScrollViewer and inside it an ItemsControl and within ItemsTemplate I have a UserControl. I want to drag that UserControl within ItemsControl. I want the ScrollViewer to scroll down, when I am dragging to the boundaries of the ItemsControl.

protected override void OnPreviewMouseMove(System.Windows.Input.MouseEventArgs e)
{
    if (this.IsMouseCaptured)
    {
        // Get the new mouse position. 
        Point mouseDragCurrentPoint = e.GetPosition(this);

        if (Math.Abs(mouseDragCurrentPoint.Y - this.ActualHeight) <= 50)
        {
            this._scrollStartOffset.Y += 5;
            _containingScrollViewer.ScrollToVerticalOffset(this._scrollStartOffset.Y);
        }
        if (mouseDragCurrentPoint.Y <= 50)
        {
            this._scrollStartOffset.Y -= 5;
            _containingScrollViewer.ScrollToVerticalOffset(this._scrollStartOffset.Y);
        }
    }
    base.OnPreviewMouseMove(e);
}

When I start dragging by calling DragDrop.DoDragDrop() scrolling don't happens. But when I disable dragging, the ScrollViewer scrolls down dependong on mouse position. Maybe there's something that I don't take into accont about dragging and Capturing the mouse? Thanks for attention. Garegin

解决方案

When using DragDrop.DoDragDrop(), I use a Sub that Handles the Me.DragOver event (in VB) so it looks as follows. Mind you, my control has a ListBox wrapped in a ScrollViewer.

Private Sub ListBox_Items_DragOver(ByVal sender As System.Object, ByVal e As System.Windows.DragEventArgs) Handles Me.DragOver
        Dim currentMousePoint As Point = e.GetPosition(_containtingScrollViewer)
        If Math.Abs(currentMousePoint.Y - _containtingScrollViewer.ActualHeight) <= 50 Then
            _containtingScrollViewer.ScrollToVerticalOffset(currentMousePoint.Y + 5)
        End If
        If currentMousePoint.Y <= 50 Then
            _containtingScrollViewer.ScrollToVerticalOffset(currentMousePoint.Y - 5)
        End If
End Sub

This gives me the ability to scroll whilst dragging items. You can tweak the tolerances to get better/smoother scrolling as needed.

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