ACC97: Listview Control Loses Data When Changing Properties

• Microsoft Access 97

SYMPTOMS

Moderate: Requires basic macro, coding, and interoperability skills.

When you toggle the Visible or Enabled properties of a ListView control, the control loses its records by approximately one-half each time those properties are cycled.

NOTE: This occurs with Microsoft ListView Control, version 5.0, which is available with Microsoft Office 97 Developer Edition Tools.

RESOLUTION

Each time you toggle the Enabled or Visible properties of the ListView control, clear the ListView control and rerun code to fill the control with data. You can use the Clear method of the ListItems collection in the control to remove all the items. The following example uses a command button to toggle the Visible property of a ListView control without losing rows of data:

1. Perform steps 1 - 7 in the "Steps to Reproduce Problem" section below.

2. Add a command button to the form. Set its Name property to Command0, and set its OnClick property to the following event procedure:

         Private Sub Command0_Click
            Dim db As Database, rs As Recordset
            Dim itmX As ListItem
            Set db = CurrentDb()
            Set rs = db.OpenRecordset("Employees", dbOpenDynaset)
   
            ' Toggle the Visible property of the control.
            Me!ListView1.Visible = Not Me!ListView1.Visible
   
            ' Clear and then refill the control with data.
            While Not rs.EOF
               Set itmX = ListView1.ListItems.Add(, , CStr(rs![FirstName] ))
               If Not IsNull(rs![LastName]) Then
                  itmX.SubItems(1) = CStr(rs![LastName])
               End If
               If Not IsNull(rs![BirthDate]) Then
                  itmX.SubItems(2) = rs![BirthDate]
               End If
               rs.MoveNext
            Wend
         End Sub
   
   

3. Save the form as frmListView, and then switch it to Form view. Note that as you click the command button to toggle the Visible property of the ListView control, the number of records displayed in the control remains the same.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Office 97 Developer Edition Tools. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The Microsoft ListView Control, version 5.0, is one of the controls included in the ActiveX control file, Comctl32.ocx. This behavior exists in version 5.00.3601 of Comctl32.ocx.

Steps to Reproduce Problem

1. Start Microsoft Access and open the sample database Northwind.mdb.

2. Create a new form not based on any table or query in Design view.

3. On the Insert menu, click ActiveX Control.

4. In the Insert ActiveX Control dialog box, select Microsoft ListView Control, version 5.0, and then click OK.

5. Set the following properties of the ListView control:

         Name: ListView1
         Width: 4"
         Height: 2"
   

6. On the View menu, click Code.

7. Type the following procedure, which populates the ListView control with data when you open the form:

         Private Sub Form_Open(Cancel As Integer)
            Dim db As Database, rs As Recordset
            Dim itmX As ListItem
            Set db = CurrentDb()
            Set rs = db.OpenRecordset("Employees", dbOpenDynaset)
   
            ListView1.ColumnHeaders.Add, , "First Name", ListView1.Width/3
            ListView1.ColumnHeaders.Add, , "Last Name", _
               ListView1.Width/3, lvwColumnCenter
            ListView1.ColumnHeaders.Add, , "Birthdate", _
               ListView1.Width/3
            ListView1.View = lvwReport
   
            While Not rs.EOF
               Set itmX = ListView1.ListItems.Add(, , CStr(rs![FirstName] ))
               If Not IsNull(rs![LastName]) Then
                  itmX.SubItems(1) = CStr(rs![LastName])
               End If
               If Not IsNull(rs![BirthDate]) Then
                  itmX.SubItems(2) = rs![BirthDate]
               End If
               rs.MoveNext
            Wend
         End Sub
   
   

8. Add a command button named Command0 to the form, and set its OnClick property to the following event procedure:

         Private Sub Command)_Click()
            Me!ListView1.Enabled = Not Me!ListView1.Enabled
         End Sub
   
   

9. Save the form as frmListView, and then switch it to Form view. Note that as you click the command button to toggle the Enabled property of the ListView control, the number of records displayed in the control reduces by about half. However, after the number of records is reduced to one, the last record continues to display even if you continue to click the command button.

REFERENCES

For more information about the ListView control, search the Help Index for "ListView control."