Question

我在表单中有几个列表框，我可以在它们之间拖放项目。代码的拖放部分似乎工作正常。将项目放入列表框后，我有一个列表框调整大小过程，并调整列表框的大小以适应其内容。我遇到的问题是，当一个项目从LB1（例如）拖到LB2时，LB1会调整大小，好像它的列表中有一个额外的项目。我想阻止这一点，但我不确定如何。这是调整大小的代码：

    Private Sub ListBox_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListBox1.MouseDown, ListBox2.MouseDown

    Dim Lbx As ListBox = sender
    Dim Pt As New Point(e.X, e.Y) ' Returns coords of mouse 
    Dim Idx As Integer
    Dim retval As DragDropEffects

    ' Determine which listbox item was dragged 
    Idx = Lbx.IndexFromPoint(Pt)

    ' Start a Drag and drop with that item 
    If Idx >= 0 Then
        ' 
        retval = Lbx.DoDragDrop(Lbx.Items(Idx), DragDropEffects.All)
        Debug.WriteLine(retval)
        If retval And DragDropEffects.Move Then
            Lbx.Items.RemoveAt(Idx)
        End If
    End If

End Sub

Private Sub ListBox_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListBox1.DragEnter, ListBox2.DragEnter
    If (e.Data.GetDataPresent(DataFormats.Text)) Then
        e.Effect = DragDropEffects.Move Or DragDropEffects.Copy
    End If
End Sub


Private Sub ListBox_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListBox1.DragDrop, ListBox2.DragDrop
    Dim LB As ListBox = sender
    LB.Items.Add(e.Data.GetData("Text"))
    QueueResize()
End Sub

以下是调整大小的代码：

    Private Sub QueueResize()
    For Each cont As System.Windows.Forms.Control In Panel1.Controls
        If cont.GetType.ToString = "System.Windows.Forms.ListBox" Then

            Dim LB As ListBox = cont
            On Error GoTo ErrHandler

            Dim lItemHeight As Long
            Dim lRet As Long
            Dim lItems As Long
            Dim sngTwips As Single
            Dim sngLBHeight As Single

            If LB.Items.Count = 0 Then
                LB.Height = 25
                'Return True

            Else
                lItems = LB.Items.Count

                lItemHeight = LB.ItemHeight
                If lItemHeight > 0 Then
                    LB.Height = lItemHeight * lItems + 5
                    'AutoSizeLBHeight = True
                End If
            End If
        End If
    Next
ErrHandler:
End Sub

任何帮助将不胜感激！提前谢谢。

Answer 1

向表单添加两个列表视图控件。将每个List View控件的AllowDrop属性设置为true。将每个列表视图控件的MultiSelect属性设置为true。将每个列表视图控件的View属性设置为List。添加以下代码：

Public Class Form1

Private Sub ListView1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListView1.DragDrop, ListView2.DragDrop
    Dim myItem As ListViewItem
    Dim myItems() As ListViewItem = e.Data.GetData("System.Windows.Forms.ListViewItem()")
    Dim i As Integer = 0

    For Each myItem In myItems
        ' Add the item to the target list.
        sender.Items.Add(myItems(i).Text)
        ' Remove the item from the source list.
        If sender Is ListView1 Then
            ListView2.Items.Remove(ListView2.SelectedItems.Item(0))
        Else
            ListView1.Items.Remove(ListView1.SelectedItems.Item(0))
        End If
        i = i + 1
    Next
End Sub

Private Sub ListView1_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles ListView1.DragEnter, ListView2.DragEnter
    ' Check for the custom DataFormat ListViewItem array.
    If e.Data.GetDataPresent("System.Windows.Forms.ListViewItem()") Then
        e.Effect = DragDropEffects.Move
    Else
        e.Effect = DragDropEffects.None
    End If
End Sub

Private Sub ListView1_ItemDrag(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemDragEventArgs) Handles ListView2.ItemDrag, ListView1.ItemDrag
    Dim myItem As ListViewItem
    Dim myItems(sender.SelectedItems.Count - 1) As ListViewItem
    Dim i As Integer = 0

    ' Loop though the SelectedItems collection for the source.
    For Each myItem In sender.SelectedItems
        ' Add the ListViewItem to the array of ListViewItems.
        myItems(i) = myItem
        i = i + 1
    Next
    ' Create a DataObject containg the array of ListViewItems.
    sender.DoDragDrop(New  _
    DataObject("System.Windows.Forms.ListViewItem()", myItems), _
    DragDropEffects.Move)
End Sub

结束班

在拖放时调整ListBox的大小

1 个答案: