VB.NET AutoResetEvent

Question

我正在嘗試了解有關事件處理的更多信息。 我嘗試在下面編寫代碼，但由於某種原因似乎無法正常工作。 我想做的是導航到一個url，等到它加載后再運行msgbox。

知道我在做什么錯嗎？

Private Shared event_1 As New AutoResetEvent(False)

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    WebBrowser1.Navigate("http://google.com")
    AddHandler WebBrowser1.DocumentCompleted, New WebBrowserDocumentCompletedEventHandler(AddressOf wb)

    event_1.WaitOne()

    MsgBox("The page is finished loading ")

End Sub

Private Sub wb(ByVal sender As Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs)
    If e.Url.AbsolutePath <> TryCast(sender, WebBrowser).Url.AbsolutePath Then
        Return
    End If
   event_1.Set()
End Sub

Answer 1

您可以像這樣在WebBrowser1對象上捕獲DocumentCompleted事件：

Private Sub webBrowser1_DocumentCompleted(ByVal sender As Object, _
    ByVal e As WebBrowserDocumentCompletedEventArgs) _
    Handles webBrowser1.DocumentCompleted

    MsgBox("THe page is loaded")

End Sub

在此處查看示例： http : //msdn.microsoft.com/zh-cn/library/system.windows.forms.webbrowser.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-2

Answer 2

發出event_1.WaitOne() ，主線程被阻止。 包括WebBrowser。 因此， event_1.Set()將永遠不會執行。

但是，您可以使用不同的方法來實現相同的行為。 不使用事件。

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Me.Enabled = False ' if you realy want to block the UI as well
    WebBrowser1.Navigate("http://www.google.com")

    Do
      Application.DoEvents()
    Loop Until WebBrowser1.ReadyState = WebBrowserReadyState.Complete

    MsgBox("The page is finished loading ")
    Me.Enabled = True ' re-enable the UI
End Sub