WPF ListView数据绑定拖放自动滚动 [英] WPF ListView Databound Drag/Drop Auto Scroll

问题描述

我一直在使用Bea的解决方案这里一段时间，它非常有帮助。问题现在我有的是，当我拖动项目或在另一个ListView控件内和我想向上/向下拖动（将项目从索引30移动到索引1）时向上/向下滚动，它不会发生。我必须拖动到ListView中的视觉项目的顶部，手动向上滚动，然后再次拖动，最终结束在我想要的位置。这不是非常用户友好。

I've been working with Bea's solution here for a while and finding it very helpful. Problem now I'm having is when I drag-n-drop items within or to another ListView control and I want to scroll up/down "during" the drag (moving an item from index 30 to index 1), it's not happening. I would have to drag to the top of the visual items in the ListView, manually scroll up, then drag again, eventually ending at the position I want. This isn't very user friendly.

现在我找到了我想要测试哪个项目被拖动的函数（DragDropHelper.DropTarget_PreviewDragOver），我会得到这个。

Now I found the function (DragDropHelper.DropTarget_PreviewDragOver) that I would want to do the testing of which item is being dragged over, and I'm getting that.

Dim pt As Point = e.GetPosition(DirectCast(Me.targetItemsControl, UIElement))

' Perform the hit test against a given portion of the visual object tree.
Dim result As HitTestResult = VisualTreeHelper.HitTest(Me.targetItemsControl, pt)

我可以得到这个视觉命中的DependencyProperty

Now from there I can get the DependencyProperty of this visual hit

Dim lvi As ListViewItem = TryCast(GetDependencyObjectFromVisualTree(TryCast(result.VisualHit, DependencyObject), GetType(ListViewItem)), ListViewItem)

这是一个ListViewItem。现在在函数DropTarget_PreviewDragOver我有DraggedItem类型Picture在Bea的例子，但是可以改变取决于您绑定到ListView的ObservableCollection。现在，我想根据鼠标在控件上的位置向上或向下拖动ListView。我尝试了下面未完成的非工作代码

Which is of a ListViewItem. Now in the function DropTarget_PreviewDragOver I have the "DraggedItem" which is of type Picture in Bea's example, but that can change depending on the ObservableCollection you have bound to the ListView. Now, I want to drag the ListView up or down depending on where the mouse is on the control. I've attempted with the below un-finished non-working code

If lvi IsNot Nothing Then
    If pt.Y <= 25 Then
        Dim lv As ListView = TryCast(targetItemsControl, ListView)
        If lv IsNot Nothing Then
            Dim index As Integer = lv.Items.IndexOf(lvi)
            If index > 1 Then
                lv.ScrollIntoView(lv.Items(index - 1))
            End If
        End If
    Else
        If pt.Y >= Me.targetItemsControl.ActualHeight - 25 Then
            Debug.Print("Scroll Down")
        End If
    End If
End If

有人指向我正确的方向，让ItemsControl或ListView在拖动项目时滚动

Can someone point me in the right direction to get this ItemsControl or ListView to scroll when dragging over the items??

谢谢！

推荐答案

我仍然在解决这个完全相同的问题。我正在使用稍微修改的Bea的拖放版本此处，这是在VB而不是C＃。当我使用ScrollIntoView如上所述，我可以向下滚动，但不能向上。所以我搞砸了，想出了这个作为我的DropTarget_PreviewDragOver：

I'm still messing around with this exact same issue too. I'm using a slightly modified version of Bea's Drag and Drop found here, which is in VB instead of C#. When I used ScrollIntoView as described above, I could scroll down but not up. So I messed around and came up with this as my DropTarget_PreviewDragOver:

 Private Sub DropTarget_PreviewDragOver(ByVal sender As Object, ByVal e As DragEventArgs)
        Dim draggedItem As Object = e.Data.GetData(Me.m_format.Name)
        Me.DecideDropTarget(e)
        If (Not draggedItem Is Nothing) Then
            If (TypeOf m_targetItemsControl Is ListBox) Then
                Dim lb As ListBox = CType(m_targetItemsControl, ListBox)
                Dim temp As Integer = m_insertionIndex
                Dim scroll As ScrollViewer = Utilities.GetScrollViewer(lb)
                If scroll.VerticalOffset = temp Then
                    temp -= 1
                End If
                If temp >= 0 And temp <= (lb.Items.Count - 1) Then
                    lb.ScrollIntoView(lb.Items(temp))
                End If
            End If
            Me.ShowDraggedAdorner(e.GetPosition(Me.m_topWindow))
            Me.UpdateInsertionAdornerPosition()
        End If
        e.Handled = True
    End Sub

我必须包含此效用函数，取自此处

and I had to include this utility function, taken from here

    Public Shared Function GetScrollViewer(ByVal listBox As ListBox)
    Dim scroll_border As Decorator = CType(VisualTreeHelper.GetChild(listBox, 0), Decorator)
    If (TypeOf scroll_border Is Decorator) Then
        Dim scroll As ScrollViewer = CType(scroll_border.Child, ScrollViewer)
        If (TypeOf scroll Is ScrollViewer) Then
            Return scroll
        Else
            Return Nothing
        End If
    Else
        Return Nothing
    End If


End Function

这是伟大的所有。然后在adorner移动的时候运行上面提到的内容，并且为了让其他人容易这样做，我在DragDropAdorner类中添加了一个变量：

which is great and all. Then running out what theuberk mentioned above with the adorner moving, and in the spirit of making this easy for someone else later, I added a variable to the DragDropAdorner class:

    Private m_mouseDelta As Point

将此添加到DragSource_PreviewMouseLeftButtonDown的最后一行：

Added this to the last line of DragSource_PreviewMouseLeftButtonDown:

        Me.m_mouseDelta = e.GetPosition(m_sourceItemContainer)

并将ShowDraggedAdorner变成：

And turned ShowDraggedAdorner into:

    Private Sub ShowDraggedAdorner(ByVal currentPosition As Point)
    If (Me.m_draggedAdorner Is Nothing) Then
        Dim adornerLayer As AdornerLayer = adornerLayer.GetAdornerLayer(Me.m_topWindow.Content)
        Me.m_draggedAdorner = New DraggedAdorner(Me.m_draggedData, DragDropBehavior.GetDragTemplate(Me.m_sourceItemsControl), m_topWindow.Content, adornerLayer)
    End If
    Me.m_draggedAdorner.SetPosition((currentPosition.X - m_mouseDelta.X), (currentPosition.Y - m_mouseDelta.Y))
    End Sub

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