DOCUMENT:Q170884 26-JUL-2002 [vbwin]
TITLE :HOWTO: Sort a ListView Control by Date
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::5.0,6.0
OPER/SYS:
KEYWORDS:kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB
======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Learning Edition for Windows, versions 6.0, 5.0
- Microsoft Visual Basic Professional Edition for Windows, versions 6.0, 5.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 6.0, 5.0
- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0
-------------------------------------------------------------------------------
SUMMARY
=======
When using a Listview control, you can set the Sorted property for the control
to sort the list alphabetically. However, the Listview control does not expose a
property or method for sorting a list by date. This article presents a method
that you can use to sort a Listview control by date.
MORE INFORMATION
================
WARNING: One or more of the following functions are discussed in this article;
VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, ObjPtr. These functions are not
supported by Microsoft Technical Support. They are not documented in the Visual
Basic documentation and are provided in this Knowledge Base article "as is."
Microsoft does not guarantee that they will be available in future releases of
Visual Basic.
To sort data in a ListView control by date, it is necessary to provide a
comparison function to the control via AddressOf.
NOTE: Using this approach, you will sort the data in the control but not the
ListItems collection. Therefore, if you must read the data from the list in
sorted order, it is necessary to step through the actual list rather than the
ListItems collection.
Step-by-Step Example
--------------------
1. Start a new Visual Basic project. Form1 is created by default.
2. On the Project menu, click Components, select the "Microsoft Windows Common
Controls 5.0" check box, and then click OK.
NOTE: You can also use Visual Basic 6.0 and select the "Microsoft Windows
Common Controls 6.0" check box with only one minor change, as noted below.
3. Add a Module to the project.
4. Draw a ListView control on Form1.
5. Add the following code to Form1:
Option Explicit
Private Sub Form_Load()
Dim clmAdd As ColumnHeader
Dim itmAdd As ListItem
'Add two Column Headers to the ListView control
Set clmAdd = ListView1.ColumnHeaders.Add(Text:="Name")
Set clmAdd = ListView1.ColumnHeaders.Add(Text:="Date")
'Set the view property of the Listview control to Report view
ListView1.View = lvwReport
'Add data to the ListView control
Set itmAdd = ListView1.ListItems.Add(Text:="Joe")
itmAdd.SubItems(1) = "05/07/97"
Set itmAdd = ListView1.ListItems.Add(Text:="Sally")
itmAdd.SubItems(1) = "04/08/97"
Set itmAdd = ListView1.ListItems.Add(Text:="Bill")
itmAdd.SubItems(1) = "05/29/97"
Set itmAdd = ListView1.ListItems.Add(Text:="Fred")
itmAdd.SubItems(1) = "05/17/97"
Set itmAdd = ListView1.ListItems.Add(Text:="Anne")
itmAdd.SubItems(1) = "04/01/97"
End Sub
' Use this line of code for Common Controls 5.0:
Private Sub ListView1_ColumnClick(ByVal ColumnHeader As _
ComctlLib.ColumnHeader)
' For Common Controls 6.0, uncomment the line below and comment the line above.
'Private Sub ListView1_ColumnClick(ByVal ColumnHeader As _
MSComctlLib.ColumnHeader)
Dim strName As String
Dim dDate As Date
Dim lngItem As Long
'Handle User click on column header
If ColumnHeader.Text = "Name" Then 'User clicked on Name header
ListView1.Sorted = True 'Use default sorting to sort the
ListView1.SortKey = 0 'items in the list
Else
ListView1.Sorted = False 'User clicked on the Date header
'Use our sort routine to sort
'by date
SendMessage ListView1.hWnd, _
LVM_SORTITEMS, _
ListView1.hWnd, _
AddressOf CompareDates
End If
'Refresh the ListView before writing the data
ListView1.Refresh
'Loop through the items in the List to print them out in
'sorted order.
'NOTE: You are looping through the ListView control because when _
'sorting by date the ListItems collection won't be sorted.
For lngItem = 0 To ListView1.ListItems.Count - 1
ListView_GetListItem lngItem, ListView1.hWnd, strName, dDate
Next
End Sub
6. Add the following code to Module1:
Option Explicit
'Structures
Public Type POINT
x As Long
y As Long
End Type
Public Type LV_FINDINFO
flags As Long
psz As String
lParam As Long
pt As POINT
vkDirection As Long
End Type
Public Type LV_ITEM
mask As Long
iItem As Long
iSubItem As Long
State As Long
stateMask As Long
pszText As Long
cchTextMax As Long
iImage As Long
lParam As Long
iIndent As Long
End Type
'Constants
Private Const LVFI_PARAM = 1
Private Const LVIF_TEXT = &H1
Private Const LVM_FIRST = &H1000
Private Const LVM_FINDITEM = LVM_FIRST + 13
Private Const LVM_GETITEMTEXT = LVM_FIRST + 45
Public Const LVM_SORTITEMS = LVM_FIRST + 48
'API declarations
Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
ByVal hWnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long
'Module Functions and Procedures
'CompareDates: This is the sorting routine that gets passed to the
'ListView control to provide the comparison test for date values.
Public Function CompareDates(ByVal lngParam1 As Long, _
ByVal lngParam2 As Long, _
ByVal hWnd As Long) As Long
Dim strName1 As String
Dim strName2 As String
Dim dDate1 As Date
Dim dDate2 As Date
'Obtain the item names and dates corresponding to the
'input parameters
ListView_GetItemData lngParam1, hWnd, strName1, dDate1
ListView_GetItemData lngParam2, hWnd, strName2, dDate2
'Compare the dates
'Return 0 ==> Less Than
' 1 ==> Equal
' 2 ==> Greater Than
If dDate1 < dDate2 Then
CompareDates = 0
ElseIf dDate1 = dDate2 Then
CompareDates = 1
Else
CompareDates = 2
End If
End Function
'GetItemData - Given Retrieves
Public Sub ListView_GetItemData(lngParam As Long, _
hWnd As Long, _
strName As String, _
dDate As Date)
Dim objFind As LV_FINDINFO
Dim lngIndex As Long
Dim objItem As LV_ITEM
Dim baBuffer(32) As Byte
Dim lngLength As Long
'
' Convert the input parameter to an index in the list view
'
objFind.flags = LVFI_PARAM
objFind.lParam = lngParam
lngIndex = SendMessage(hWnd, LVM_FINDITEM, -1, VarPtr(objFind))
'
' Obtain the name of the specified list view item
'
objItem.mask = LVIF_TEXT
objItem.iSubItem = 0
objItem.pszText = VarPtr(baBuffer(0))
objItem.cchTextMax = UBound(baBuffer)
lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _
VarPtr(objItem))
strName = Left$(StrConv(baBuffer, vbUnicode), lngLength)
'
' Obtain the modification date of the specified list view item
'
objItem.mask = LVIF_TEXT
objItem.iSubItem = 1
objItem.pszText = VarPtr(baBuffer(0))
objItem.cchTextMax = UBound(baBuffer)
lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _
VarPtr(objItem))
If lngLength > 0 Then
dDate = CDate(Left$(StrConv(baBuffer, vbUnicode), lngLength))
End If
End Sub
'GetListItem - This is a modified version of ListView_GetItemData
' It takes an index into the list as a parameter and returns
' the appropriate values in the strName and dDate parameters.
Public Sub ListView_GetListItem(lngIndex As Long, _
hWnd As Long, _
strName As String, _
dDate As Date)
Dim objItem As LV_ITEM
Dim baBuffer(32) As Byte
Dim lngLength As Long
'
' Obtain the name of the specified list view item
'
objItem.mask = LVIF_TEXT
objItem.iSubItem = 0
objItem.pszText = VarPtr(baBuffer(0))
objItem.cchTextMax = UBound(baBuffer)
lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _
VarPtr(objItem))
strName = Left$(StrConv(baBuffer, vbUnicode), lngLength)
'
' Obtain the modification date of the specified list view item
'
objItem.mask = LVIF_TEXT
objItem.iSubItem = 1
objItem.pszText = VarPtr(baBuffer(0))
objItem.cchTextMax = UBound(baBuffer)
lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _
VarPtr(objItem))
If lngLength > 0 Then
dDate = CDate(Left$(StrConv(baBuffer, vbUnicode), lngLength))
End If
End Sub
7. Save your project.
8. Press the F5 key to run the application. Click the Date column header to sort
the items in the list by date.
Additional query words:
======================================================================
Keywords : kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVB500 kbVB600 kbZNotKeyword3
Version : :5.0,6.0
Issue type : kbhowto
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 2002.