Question

我正在编写一个涉及RFID和RFID的应用程序。条码扫描仪。我正在尝试为RFID扫描仪创建一个类。继续得到这个＆amp;％＃$ *错误。

以下是相关代码：

Private Dispatcher As Dispatcher
Private Delegate Sub TimerDispatcherDelegate()

...

  '[Constructor]
    'Start timer
    timer = New System.Timers.Timer()
    AddHandler timer.Elapsed, AddressOf timer_Elapsed
    timer.Interval = 1000
    timer.Enabled = True
  End If

End Sub


Private Sub timer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs)

  'Delegate handler for timer events
  ***NEXT LINE THROWS THE ERROR- Me.Dispatcher is not set to an instance of an object***
  Me.Dispatcher.Invoke(Windows.Threading.DispatcherPriority.Normal, New TimerDispatcherDelegate(AddressOf timer_WorkItem))

End Sub


Private Sub timer_WorkItem()

  'Populate reader struct
  ReaderState.Name = ReaderName
  ReaderState.CurrentState = SmartCard.SCARD_STATE_UNAWARE
...

我很难过。如果我拿出Dispatcher声明，我会收到“Me.Dispatcher不是成员”错误。

但是，我（无耻地）从制造商的演示应用程序中获取代码＆amp;它使用相同的timer_Elapsed（...）代码 - 项目中没有Dispatcher声明 - 运行得很好。

有什么想法吗？

VB.Net Dispatcher“NullReferenceException”错误

0 个答案: