Question

我有一个mousemove事件处理程序附加到Excel UserForm中名为lstUneditedStudents的3列列表框。绑定列为数字1.该列包含字母数字字符串，如“A202H”。为什么我在此代码中使用Null无效？（ErrorLog是我自己的类，它将错误记录到工作表中。这很顺利，在我调试时记录我的错误。）

Private Sub lstUneditedStudents_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
    On Error Resume Next
    If Button = 1 Then
        Dim dob As DataObject, listValue As String
        listValue = lstUneditedStudents.value
        If listValue <> "" Then
            Set dob = New DataObject
            dob.SetText listValue
            dob.StartDrag
        End If
    End If
    If Err.Number <> 0 Then
        Dim errLog As New ErrorLog
        errLog.Log "frmEditClasses", "lstUneditedStudents_MouseMove", Err.Source, Err.Description, Err.Number
    End If
End Sub

当您单击列表框时，会出现恼人的延迟，然后在重新填充之前列表框变为空白。一旦你让它稳定下来，拖动工作和其他子程序处理从这个列表框到另一个列表框的移动。但是，仍然会出现此错误。

Answer 1

我认为你只需要在将它赋给变量之前检查lstUneditedStudents.value是否为null。例如：

Private Sub lstUneditedStudents_MouseMove(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)
    On Error Resume Next
    If Button = 1 Then
        Dim dob As DataObject, listValue As String
        If Not IsNull(lstUneditedStudents.value) Then
            listValue = lstUneditedStudents.value
            If listValue <> "" Then
                Set dob = New DataObject
                dob.SetText listValue
                dob.StartDrag
            End If
        End If
    End If
    If Err.Number <> 0 Then
        Dim errLog As New ErrorLog
        errLog.Log "frmEditClasses", "lstUneditedStudents_MouseMove", Err.Source, Err.Description, Err.Number
    End If
End Sub

在Excel中的MouseMove事件处理程序中无效使用空错误94的原因是什么

1 个答案: