HOWTO: Use a ComboBox to Enter Data into a FlexGrid Control

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

You can use a ComboBox that appears over the active cell to make it easier to enter data into a MSFlexGrid or MSHFlexGrid control. This article demonstrates how to do this, as well as how to resize the ComboBox when a column is resized. Please note that you can only adjust the width of the ComboBox.

The subclassing (or hook) of the FlexGrid control is optional. Its purpose in this article is to resize the ComboBox dynamically when a column in the FlexGrid is resized.

MORE INFORMATION

Steps to Create Sample Project

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.



2. On the Project menu, click Components, select Microsoft FlexGrid Control, and click OK.



3. Add a ComboBox and MSFlexGrid control to Form1.



4. Place the following code into the Form's module:
   

   
         Option Explicit
   
         Private Sub Form_Unload(Cancel As Integer)
             If IsHooked Then
                Unhook   ' Stop checking messages.
             End If
         End Sub
   
         Private Sub MSFlexGrid1_MouseUp(Button As Integer, _
            Shift As Integer, x As Single, y As Single)
             Static CurrentWidth As Single
             ' Check to see if the Cell's width has changed.
             If MSFlexGrid1.CellWidth <> CurrentWidth Then
                 Combo1.Width = MSFlexGrid1.CellWidth
                 CurrentWidth = MSFlexGrid1.CellWidth
             End If
         End Sub
   
         Private Sub Form_Load()
             gHW = MSFlexGrid1.hWnd
             Hook   ' Start checking messages.
             MSFlexGrid1.AllowUserResizing = flexResizeColumns
             MSFlexGrid1.Cols = 4
             MSFlexGrid1.Rows = 6
             MSFlexGrid1.RowHeightMin = Combo1.Height
             Combo1.Visible = False
             Combo1.ZOrder (0)
             Combo1.Width = MSFlexGrid1.CellWidth
             ' Load the ComboBox's list.
             Combo1.AddItem "Some text"
             Combo1.AddItem "Some more text"
             Combo1.AddItem "Still more text"
             Combo1.AddItem "Yet even more text"
             Combo1.AddItem "Way more text than that"
         End Sub
   
   
         Private Sub MSFlexGrid1_Click()
             ' Position and size the ComboBox, then show it.
             Combo1.Width = MSFlexGrid1.CellWidth
             Combo1.Left = MSFlexGrid1.CellLeft + MSFlexGrid1.Left
             Combo1.Top = MSFlexGrid1.CellTop + MSFlexGrid1.Top
             Combo1.Text = MSFlexGrid1.Text
             Combo1.Visible = True
         End Sub
   
         Private Sub Combo1_Click()
             ' Place the selected item into the Cell and hide the ComboBox.
             MSFlexGrid1.Text = Combo1.Text
             Combo1.Visible = False
         End Sub 




5. On the Project menu, add a new Module and insert the following code:
   

   
         Option Explicit
   
         Declare Function CallWindowProc Lib "user32" Alias _
            "CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
            ByVal hWnd As Long, ByVal Msg As Long, _
            ByVal wParam As Long, ByVal lParam As Long) As Long
   
         Declare Function SetWindowLong Lib "user32" Alias _
            "SetWindowLongA" (ByVal hWnd As Long, _
            ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
   
         Private Const GWL_WNDPROC = -4
         Private IsHooked As Boolean
         Private Const WM_SIZE = &H5
         Private Const WM_PAINT = &HF
         Private lpPrevWndProc As Long
         Public gHW As Long
   
         Public Sub Hook()
             If IsHooked Then
             ' Do not hook it twice without unhooking,
             ' or you will not be able to unhook it.
             Else
             lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
                AddressOf WindowProc)
             IsHooked = True
             End If
         End Sub
   
         Public Sub Unhook()
             Dim temp As Long
             temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
             IsHooked = False
         End Sub
   
         Function WindowProc(ByVal hw As Long, ByVal uMsg As _
            Long, ByVal wParam As Long, ByVal lParam As Long) As Long
             WindowProc = CallWindowProc(lpPrevWndProc, hw, _
                uMsg, wParam, lParam)
             ' The interior of the control is repainted, but not resized.
             If uMsg = WM_SIZE Or uMsg = WM_PAINT Then
                Form1.Combo1.Width = Form1.MSFlexGrid1.CellWidth
                Form1.Combo1.Left = Form1.MSFlexGrid1.CellLeft + _
                   Form1.MSFlexGrid1.Left
                Form1.Combo1.Top = Form1.MSFlexGrid1.CellTop + _
                   Form1.MSFlexGrid1.Top
             End If
         End Function 




6. On the File menu, click Save and build an executable. Please do not ignore this step. The use of AddressOf in the IDE can cause the system to crash. Please see the REFERENCES section of this article for more information about this issue.



7. Run the EXE and click in a cell of the FlexGrid. The ComboBox should appear and cover the cell. With the ComboBox showing, use the mouse to widen that column. When you release the mouse button the ComboBox should also adjust in size. This is handled by the code that hooks into the Window's messages. When you select from the ComboBox's list, your choice is added to the cell.

REFERENCES

For additional information, please see the following article in the Microsoft Knowledge Base:

Q168795 HOWTO: Hook Into a Window's Messages Using AddressOf

© Microsoft Corporation 1999, All Rights Reserved.
Contributions by Chris E. Jolley, Microsoft Corporation

Additional query words:

Keywords : kbAPI kbComboBox kbCtrl kbGrpUser kbVBp500 kbVBp600 kbGrpVB
Version : WINDOWS:5.0,6.0
Platform : WINDOWS
Issue type : kbhowto