我想在treeview上实现拖放操作,也就是把一个node拖放到另外一个node前面,或者后面,或者里面,我看很多例子上就是采用object.drag vbbegindrag,但是进行拖放以后好像没有效果,该交换位置的没有交换位置,这是怎么回事啊,我问了别人他们都说拖放过程可以由treeview自动完成,不需要自己写代码交换位置,到底应该怎么实现,请各位大虾不吝赐教啊,谢谢谢谢
调试欢乐多
Data As MSComctlLib.DataObject, _
AllowedEffects As Long)
Data.Clear
If Not Me.SmartTreeView.SelectedItem Is Nothing Then
Data.SetData Me.SmartTreeView.SelectedItem.Key,vbCFText
End If
End Sub OLEStartDrag事件句柄把Data参数设置成被拖放节点的Key属性,稍后我们可以看到这个值的用处。当用户用鼠标拖着节点移动,VB触发OLEDragOver事件,下面给出了事件句柄的代码。当用户拖着节点经过其他节点时,其他节点不会自动以高亮度颜色显示,所以我们必须将TreeView控件的DropHighlight属性设置到适当的节点,以表明鼠标当前正处在该节点的位置上。鼠标所在位置的节点可通过控件的HitTest方法获知,HitTest方法的参数是指针的坐标。Private Sub SmartTreeView_OLEDragOver _
(Data As MSComctlLib.DataObject, Effect As Long, _
Button As Integer, Shift As Integer, x As Single, _
y As Single, State As Integer) With SmartTreeView
If State = vbLeave Then
Set .DropHighlight = Nothing
Else
.DropHighlight = .HitTest(x, y)
End If
End With
mfX = x
mfY = y
If y > 0 And y < 100 Then
m_iScrollDir = -1
Timer1.Enabled = True
ElseIf y > (SmartTreeView.Height - 200) And _
y < SmartTreeView.Height Then
m_iScrollDir = 1
Timer1.Enabled = True
Else
Timer1.Enabled = False
End If
End Sub 拖着节点经过其他可见的节点不存在什么问题,但要把节点拖到某个当前不在控件可见区域的节点就要复杂一些。为了实现这个功能,当鼠标拖着节点到达TreeView控件的顶部或底部时,我们必须强制TreeView滚动其可见区域。TVEdit工程利用了一个每200ms触发的Timer,以便分析当前鼠标指针所处的位置。如果鼠标拖着节点到达距离TreeView控件顶部或底部100 pixel的位置,控件显示的内容就必须滚动。有关这一技术的详细说明,有兴趣的读者可参见MSDN文章Q177743。 SmartTreeView_OLEDragOver事件句柄有几行代码用来判断是否要滚动控件以及开启Timer,但实际的滚动操作由Timer的事件句柄完成。 当用户拖着节点到达目的地后放开鼠标键,控件触发OLEDragDrop事件,这个事件句柄要提取出被拖动的节点,并把它放在当前高亮度显示的节点之下。前面我们把被拖动节点的Key放入了事件句柄的参数Data对象,现在可以利用这个Key方便地从Notes集合得到被拖动的节点,只要把这个节点的ParentNode属性设置成当前高亮度显示的节点,就完成了移动节点(及其所有子节点)的操作。注意被拖动的节点不能放入它自己的子节点之下,因为这会形成父子节点相互引用的循环引用关系。Private Sub SmartTreeView_OLEDragDrop( _
Data As MSComctlLib.DataObject, Effect As Long, _
Button As Integer, Shift As Integer, x As Single, _
y As Single) Dim strKey As String
Dim thisNode, DragNode As Node Set oNode = Me.SmartTreeView.HitTest(x, y) If Data.GetFormat(vbCFText) Then
strKey = Data.GetData(vbCFText)
Set oDragNode = SmartTreeView.Nodes(strKey)
On Error Resume Next
Set oDragNode.Parent = oNode
If Err.Number = 35614 Then
MsgBox "节点不能移动到此位置:不能创建循环引用关系。"
On Error GoTo 0
End If
Set SmartTreeView.DropHighlight = Nothing
End If
End Sub
Dim objT1 As Node, objT2 As Node
Dim I As Long
With Me.TreeView1
Set objT1 = .Nodes.Add(, , "Root", "Root")
Set objT2 = .Nodes.Add(, , "最后一个", "最后一个")
Set objT2.Parent = objT1
For I = 10 To 1 Step -1
Set objT2 = .Nodes.Add(, , "第 " & I & "个", "第 " & I & "个")
Set objT2.Parent = objT1
Next
End With
End SubPrivate Sub TreeView1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
Dim objT As Node
Set objT = Me.TreeView1.HitTest(x, y)
If Not objT Is Nothing Then
Set objNodeOLESource = objT
' objT.Selected = True
End If
End SubPrivate Sub TreeView1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
Dim aaNode As Node
End SubPrivate Sub TreeView1_OLEDragDrop(Data As MSComctlLib.DataObject, Effect As Long, Button As Integer, Shift As Integer, x As Single, y As Single)
Dim objP As Node
Dim strKey As String
Dim strText As String
Dim objT As Node
Set objP = Me.TreeView1.HitTest(x * Screen.TwipsPerPixelX, y * Screen.TwipsPerPixelY)
If Not objP Is Nothing Then
If Not objNodeOLESource Is Nothing Then
strKey = objNodeOLESource.Key
If strKey = objP.Key Then
Exit Sub
End If
strText = objNodeOLESource.Text
Me.TreeView1.Nodes.Remove objNodeOLESource.Index
Set objT = Me.TreeView1.Nodes.Add(objP.Index, , strKey, strText)
End If
End If
End SubPrivate Sub TreeView1_OLEDragOver(Data As MSComctlLib.DataObject, Effect As Long, Button As Integer, Shift As Integer, x As Single, y As Single, State As Integer)
Set Me.TreeView1.DropHighlight = Me.TreeView1.HitTest(x * Screen.TwipsPerPixelX, y * Screen.TwipsPerPixelY)
'Set Me.TreeView1.DropHighlight = Me.TreeView1.HitTest(x, y)
End Sub
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