示例：处理标签更改事件

本示例阐述了如何在标签值或标签的质量发生变化时获取事件。第一个子程序创建了 TagGroup 对象，并对其添加了标签并激活 TagGroup。第二个子程序处理 TagGroup 更改事件，并为 TagGroup 对象中标签的值或质量发生变化的每个标签记录消息。
Public WithEvents oGroup As TagGroup
Private Sub Button1_Released()
  Dim TagsInError As StringList
  On Error GoTo errHandler
  If oGroup Is Nothing Then
    Set oGroup = Me.Application.CreateTagGroup(Me.AreaName, 500)
    oGroup.Add "system\Second"
    oGroup.Add "system\Minute"
    oGroup.Active = True
    'after setting tag group active, use RefreshFromSource() method before any tag reads or writes
    oGroup.RefreshFromSource TagsInError
  End If
  Exit Sub
errHandler:
  LogDiagnosticsMessage "VBA Error in SetUpTagGroup(). Error:  " & Hex(Err.Number) & " - " & Err.Description, ftDiagSeverityError
  'can add code to handle any specific errors
End Sub
Private Sub Display_Unload()
  'ensure object memory is released when closing display
  Set oGroup = Nothing
End Sub
Private Sub oGroup_Change(ByVal TagNames As IGOMStringList)
' the Change()event can occur if the tag value and/or quality changes
  Dim vTagName As Variant
  Dim vValue As Variant
  Dim TimeStamp As Date
  Dim cQuality As tagQualityConstants
  Dim cSubStatus As tagSubStatusConstants
  Dim cLimit As tagLimitConstants
  Dim sQuality As String
  Dim oTag As Tag
  'error handling added as error can be encountered during tag read
  On Error GoTo errHandler
  For Each vTagName In TagNames
    Set oTag = oGroup.Item(vTagName)
    'reading only value
    vValue = oTag.Value
    'reading tag value and other tag info such as Quality
    oTag.GetTagData vValue, TimeStamp, cQuality, cSubStatus, cLimit
    Select Case cQuality
    Case 0
      sQuality = "Bad"
    Case 1
      sQuality = "Uncertain"
    Case 2
      sQuality = "Good"
    End Select
    If VarType(vValue) <> vbEmpty Then
      LogDiagnosticsMessage "Tag " & oTag.Name & " value = " & vValue & " Quality: " & sQuality
    Else
      LogDiagnosticsMessage "Unable to read value of tag " & oTag.Name & ". The quality of the value is " & sQuality, ftDiagSeverityWarning
    End If
  Next
  Exit Sub
errHandler:
  LogDiagnosticsMessage "VBA Error in oGroup_Change(). Error:  " & Hex(Err.Number) & " - " & Err.Description, ftDiagSeverityError
  'can add code to handle any specific errors
End Sub
提供反馈
对本文档有问题或反馈吗？ 请在这里提交您的反馈 。
Normal