BUG:TreeView: NodeCheck Event Does Not Occur

BUG: TreeView: NodeCheck Event Does Not Occur

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This article was previously published under Q221557

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SYMPTOMS



RESOLUTION


Step by Step Example



STATUS



MORE INFORMATION


Steps to Reproduce Behavior



REFERENCES

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SYMPTOMS
When a TreeView control with the Checkboxes property set to True is placed on a...

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When a TreeView control with the Checkboxes property set to True is placed on a form and the user presses the left-mouse button over a checkbox and then drags the mouse away from the checkbox before releasing the mouse button, the state of the checkbox is toggled, but a NodeCheck event does not occur.


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RESOLUTION
You can work around the problem by programmatically ensuring that the event occu...

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You can work around the problem by programmatically ensuring that the event occurs if the mouse has been dragged away from the checkbox.


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Step by Step Example

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Open a new Visual Basic Standard Exe project. Form1 is created by default.
On the Project menu, click Components. Select Microsoft Common Controls 6.0 and click OK.
Add a TreeView control to Form1.
Add the following code to the General Declarations section of Form1:

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
lParam As Any) As Long   ' <---

' treeview messages
Private Const TV_FIRST = &H1100
' wParam = 0, lParam = lptvhti, rtns hItem
Private Const TVM_HITTEST = (TV_FIRST + 17)

Private Type POINTAPI   ' pt
x As Long
y As Long
End Type

' structure passed with the TVM_HITTEST message
Private Type TVHITTESTINFO
pt As POINTAPI
flags As Long
hItem As Long
End Type

' TVHITTESTINFO.flags value. An item's checkbox
' is in fact held in the item's state icon image.
Private Const TVHT_ONITEMSTATEICON = &H40

Private m_nodChecked As Node

Private Sub Form_Load()
Dim Node1 As Node
Dim Node2 As Node
Dim Node3 As Node
Dim i As Integer
Dim j As Integer
Dim k As Integer
' For some convenience...
With TreeView1
.HideSelection = False
.Indentation = 19 * Screen.TwipsPerPixelX
.LabelEdit = tvwManual
.LineStyle = tvwRootLines
.Checkboxes = True
End With

' Fill up the treeview...
For i = 1 To 2
Set Node1 = TreeView1.Nodes.Add(, , , "Root" & i)
For j = 1 To 3
Set Node2 = TreeView1.Nodes.Add(Node1.Index, tvwChild, , _
"Root" & i & "Child" & j)
For k = 1 To 3
Set Node3 = TreeView1.Nodes.Add(Node2.Index, tvwChild, , _
"GrandChild" & (16 * (i - 1)) + (4 * (j - 1)) + k)
Next k
Next j
Node1.Expanded = True
Next i
End Sub

Private Sub TreeView1_MouseDown(Button As Integer, Shift As Integer, _
x As Single, y As Single)
Dim tvhti As TVHITTESTINFO

Debug.Print "MouseDown: " & Button & " " & Shift & "  " & _
x & " " & y

If (Button = vbLeftButton) Then
' determine if the mouse pointer is being depressed over the Node's
' checkbox (assumes that the Form's ScaleMode is set to vbTwips).
tvhti.pt.x = x / Screen.TwipsPerPixelX
tvhti.pt.y = y / Screen.TwipsPerPixelY
If (SendMessage(TreeView1.hWnd, TVM_HITTEST, 0, tvhti)) Then

If (tvhti.flags And TVHT_ONITEMSTATEICON) Then
' the value of the Node's Checked property will be toggled
' *after* this procedure finishes execution.
Set m_nodChecked = TreeView1.HitTest(x, y)
End If

End If   ' TVM_HITTEST
End If   ' (Button = vbLeftButton)
End Sub

Private Sub TreeView1_NodeCheck(ByVal Node As MSComctlLib.Node)

If (Node Is m_nodChecked) Then

' Either the left-mouse button is being released over the Node
' whose checkbox has been toggled, or this event procedure
' is being called from TreeView1_MouseUp. This *is* where we
' want to process code...
Debug.Print "NodeCheck: " & m_nodChecked & _
".Checked = " & m_nodChecked.Checked & _
vbCrLf & vbTab & " (do process code here)"

' De-reference the module level Node variable so you don't
' call this event again in TreeView1_MouseUp.
Set m_nodChecked = Nothing

Else
' This event is being raised by the TreeView because the mouse
' pointer is being released over a node whose checkbox state
' has *not* been toggled. you do *not* want to process code here...
Debug.Print "NodeCheck: " & Node & _
".Checked = " & Node.Checked & _
vbCrLf & vbTab & " (do *not* process code here)"

End If
End Sub

Private Sub TreeView1_MouseUp(Button As Integer, Shift As Integer, _
x As Single, y As Single)

If (m_nodChecked Is Nothing) = False Then

' You didn't get a NodeCheck event (the variable is still set),
' the mouse pointer is *not* over the Node whose checkbox
' state has been toggled. Explicitly call the event procedure.
Call TreeView1_NodeCheck(m_nodChecked)

End If

Debug.Print "MouseUp: " & Button & " " & Shift & " " & _
x & " " & y
End Sub

Run the program and position the mouse cursor over a checkbox. Press and hold down the left-mouse button, drag the mouse cursor away from the checkbox, and then release the mouse button. Note that a message verifying that the NodeCheck event occurred is printed in the Immediate pane.



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STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are li...

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Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.


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MORE INFORMATION
Steps to Reproduce Behavior Open a new Visual Basic Standard Exe project. Form1...

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Steps to Reproduce Behavior

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Open a new Visual Basic Standard Exe project. Form1 is created by default.
On the Project menu, click Components. Select Microsoft Common Controls 6.0 and click OK.
Add a Treeview control to Form1. Open the Treeview control's property page by right-clicking on the control and clicking Properties. Check the Treeview control's Checkboxes property and click OK.
Add the following code to the General Declarations section of Form1:

Private Sub Form_Load()
Dim Node1 As Node
Dim Node2 As Node
Dim Node3 As Node
Dim i As Integer
Dim j As Integer
Dim k As Integer

' For some convenience...
With TreeView1
.HideSelection = False
.Indentation = 19 * Screen.TwipsPerPixelX
.LabelEdit = tvwManual
.LineStyle = tvwRootLines
End With

' Fill up the treeview...
For i = 1 To 2
Set Node1 = TreeView1.Nodes.Add(, , , "Root" & i)
For j = 1 To 3
Set Node2 = TreeView1.Nodes.Add(Node1.Index, tvwChild, , _
"Root" & i & "Child" & j)
For k = 1 To 3
Set Node3 = TreeView1.Nodes.Add(Node2.Index, tvwChild, , _
"GrandChild" & (16 * (i - 1)) + (4 * (j - 1)) + k)
Next k
Next j
Node1.Expanded = True
Next i
End Sub

Private Sub TreeView1_NodeCheck(ByVal Node As MSComctlLib.Node)
Debug.Print "NodeCheck Event"
End Sub

Run the program. Position the mouse cursor over a checkbox, press and release the left-mouse button on the checkbox, and note that the message is printed in the Immediate pane.
Position the mouse cursor over a checkbox, and press and hold down the left-mouse button. Drag the mouse cursor away from the checkbox and then release the mouse button. Note that no message appears.



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http://support.microsoft.com/kb/221557/en-us/