Question

我试图从UWP类库后台任务中引发事件，但我需要在UWP应用程序中的主UI线程上封送它，我计划使用类库。我正在寻找一种方法来从后台任务中编组它。我查看过几篇文章，包括这篇文章： Raise Events in .NET on the main UI thread 但它对我没有意义。任何人都可以帮我解决下面的代码吗？

    Private ReceiveTask As New Task(Sub()    
                                    Dim InStream As Stream = CSocket.InputStream.AsStreamForRead    
                                    While killswitch = False    
                                        Try    
                                            Dim Reader As StreamReader = New StreamReader(InStream)    
                                            Dim DataText As String = ""    
                                            While Reader.Peek <> -1    
                                                DataText &= Convert.ToChar(Reader.Read)    
                                            End While    
                                            RaiseEvent DataReceived(DataText)    
                                        Catch ex As Exception    
                                            RaiseEvent SocketError("Receiving", ex.Message)    
                                        End Try    
                                    End While    
                                End Sub)

感谢jmcilhinney，以下代码有效！

    Private ReceiveTask As New Task(Sub()
                                    Dim InStream As Stream = CSocket.InputStream.AsStreamForRead
                                    While killswitch = False
                                        Try
                                            Dim Reader As StreamReader = New StreamReader(InStream)
                                            If Reader.Peek <> -1 Then
                                                DataText = ""
                                                While Reader.Peek <> -1
                                                    DataText &= Convert.ToChar(Reader.Read)
                                                End While
                                                uiContext.Post(AddressOf RaiseDataToUI, Nothing)
                                            End If
                                        Catch ex As Exception
                                            ReceiveError = ex.Message
                                            uiContext.Post(AddressOf RaiseErrorToUI, Nothing)
                                        End Try
                                    End While
                                End Sub)

Answer 1

我自己没有做任何UWP开发，但我相信正确的方法是使用SynchronizationContext类，就像在WPF中一样。原则是SynchronizationContext.Current属性将产生类的线程特定实例，因此您可以在UI线程上获取该属性的值，然后在其他地方使用该对象来编组对拥有线程的调用。通常在UI线程上创建的对象的构造函数中检索属性值，例如

Imports System.Threading

Public Class SomeClass

    'Get the context for the thread on which the current instance is created.
    Private uiContext As SynchronizationContext = SynchronizationContext.Current

    Private Sub ThisMethodIsCalledOnASecondaryThread()
        uiContext.Post(AddressOf ThisMethodIsCalledOnTheUIThread, Nothing)
    End Sub

    Private Sub ThisMethodIsCalledOnTheUIThread(data As Object)
        'Execute UI thread logic here, e.g. raise an event.
    End Sub

End Class

如何从UWP APP（vb.net）中的后台任务在主UI线程上引发事件

1 个答案: