Q269783: BUG: Cannot Drag Multiple Selections from ListView Control
Article: Q269783
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s):
Keyword(s): kbCtrl kbDragDrop kbListView kbVBp kbVBp600bug kbGrpDSVB kbDSupport kbCodeSnippet
Last Modified: 12-MAY-2001
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The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
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SYMPTOMS
========
If you use the Drag method to implement the drag-and-drop feature for a ListView
control, the application works as expected when you use the Visual Basic 5.0
version of the ListView control. However, when you use the Visual Basic 6.0
version of the ListView control, you can only drag one item, even if you select
multiple items.
CAUSE
=====
When the Drag method is called, the ListView control updates the selection state
so that only the item that is clicked most recently is selected.
RESOLUTION
==========
To work around this problem, store the selection information before the Drag
method is called, and restore the selection state after the Drag method is
issued. You need to restore the selection state after the function that calls
the Drag method exits. For sample code that demonstrates this workaround, see
the "More Information" section.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.
MORE INFORMATION
================
Steps to Reproduce Behavior
---------------------------
1. Create a Standard EXE project in Visual Basic 6.0. Form1 is created by
default.
2. Press CTRL+T. In the Components dialog box, select the "Microsoft Windows
Common Controls 6.0" check box, and then click OK.
3. Add a ListView control (ListView1) and a Label control (Label1) to Form1.
Enlarge both controls.
4. Add the following code to Form1:
Option Explicit
Private m_bBegDrag As Boolean
Private Sub ListView1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
If m_bBegDrag = True Then
ListView1.Drag vbBeginDrag
m_bBegDrag = False
End If
End Sub
Private Sub Form_Load()
Dim ItmX As ListItem
Dim i As Integer
Label1.BorderStyle = vbFixedSingle
ListView1.View = lvwList
ListView1.MultiSelect = True
For i = 1 To 12
Set ItmX = ListView1.ListItems.Add(, , "Item " & CStr(i))
Next
End Sub
Private Sub Label1_DragDrop(Source As Control, x As Single, y As Single)
Dim nCount As Integer
Dim ItmX As ListItem
If Not TypeOf Source Is ListView Then Exit Sub
For Each ItmX In Source.ListItems
If ItmX.Selected = True Then
nCount = nCount + 1
End If
Next
MsgBox nCount & " Items dropped"
End Sub
Private Sub ListView1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
If Not ListView1.HitTest(x, y) Is Nothing Then
m_bBegDrag = True
End If
End Sub
Private Sub ListView1_MouseUp(Button As Integer, Shift As Integer, x As Single, y As Single)
m_bBegDrag = False
End Sub
5. Press F5 to run the application. Select several items in the ListView
control, and drag them to the Label control. Notice that only one item is
dropped to the Label control.
Workaround
----------
Continuing from the previous steps, follow these steps to work around this
problem:
1. From the Project menu, click Add Module. In the Add Module dialog box, click
Open. Module1 is added to your project.
2. Add the following code to Module1:
Option Explicit
Public Sub GetSelectedItems(lvwCtl As ListView, colItems As Collection, & _
x As Single, y As Single)
Dim i As Integer
Dim ItmX As ListItem
' Clear the collection
Set colItems = New Collection
' If you click a non-selected node, you only drag this node.
If lvwCtl.HitTest(x, y).Selected = False Then
colItems.Add (lvwCtl.HitTest(x, y).Index)
Exit Sub
End If
' Otherwise, drag the currently selected nodes.
For Each ItmX In lvwCtl.ListItems
If ItmX.Selected = True Then
colItems.Add (ItmX.Index)
End If
Next
End Sub
Public Sub SetSelectedItems(lvwCtl As ListView, colItems As Collection)
Dim i As Integer
Dim ItmX As ListItem
If colItems Is Nothing Then Exit Sub
If colItems.Count = 0 Then Exit Sub
' Select the items that should be selected.
For i = 1 To colItems.Count
lvwCtl.ListItems(colItems(i)).Selected = True
Next
End Sub
3. Replace this code in Form1
Private Sub ListView1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
If m_bBegDrag = True Then
ListView1.Drag vbBeginDrag
m_bBegDrag = False
End If
End Sub
with the following code:
Private m_bSetSelectedItems As Boolean
Private m_colItems As Collection
Private Sub ListView1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
If m_bBegDrag = True Then
GetSelectedItems ListView1, m_colItems, x, y
ListView1.Drag vbBeginDrag
m_bBegDrag = False
m_bSetSelectedItems = True
End If
End Sub
Private Sub ListView1_DragOver(Source As Control, x As Single, y As Single, State As Integer)
If m_bSetSelectedItems Then
SetSelectedItems ListView1, m_colItems
m_bSetSelectedItems = False
End If
End Sub
4. Press F5 to run the application. Select several items in the ListView
control, and drag them to the Label control. Note that all of the selected
items are dropped as expected.
Additional query words:
======================================================================
Keywords : kbCtrl kbDragDrop kbListView kbVBp kbVBp600bug kbGrpDSVB kbDSupport kbCodeSnippet
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version : :6.0
Issue type : kbbug
Solution Type : kbpending
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