VB.NET WPF线程

Question

我对VB.NET和WPF比较陌生，我有一个基本的线程问题。

我只想弄清楚如何在使用NavigationService的页面内使用Timer。以下是我有：

Public Class SplashPage 
    Inherits Page 

    Public Sub New(ByVal oData As Object) 

     StartTimer(5000) 

    End Sub 

    Public Sub StartTimer(ByVal iInterval As Double) 

     Dim timeoutTimer As New System.Timers.Timer 

     timeoutTimer.Interval = 5000 
     timeoutTimer.Enabled = True 

     'Function that gets called after each interval 
     AddHandler timeoutTimer.Elapsed, AddressOf OnTimedEvent 

    End Sub 

    Public Sub OnTimedEvent(source As Object, e As System.Timers.ElapsedEventArgs) 

     If NavigationService.CanGoBack Then 
      NavigationService.GoBack() 
     End If 

     'MessageBox.Show(e.SignalTime) 

    End Sub 

End Class 

的NavigationService.CanGoBack语句导致错误消息：“因为不同的线程拥有它调用线程不能访问此对象”

任何意见或建议，将不胜感激。谢谢！

• MG

Answer 1

这里的问题是，你不能从后台线程触摸UI元素。在这种情况下，Timer.Elapsed事件在后台线程中触发，当您触摸UI时会出错。你需要触摸元素

Private context = SynchronizationContext.Current 
Public Sub OnTimedEvent(source As Object, e As System.Timers.ElapsedEventArgs) 
    context.Post(AddressOf OnTimerInMainThread, e) 
End Sub 

Private Sub OnTimerInMainThread(state as Object) 
    Dim e = CType(state, ElapsedEventArgs) 
    If NavigationService.CanGoBack Then 
    NavigationService.GoBack() 
    End If 

    MessageBox.Show(e.SignalTime) 
End Sub