关于回调的问题

[水晶烟灰缸]

    Public Delegate Function VideoStreamCallback(ByVal hwnd As Integer, ByRef lpVHdr As VIDEOHDR) As Boolean
    Public Declare Function SendVideoStreamCallbackMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As VideoStreamCallback) As Integer

    Public Function HandleVideoStreamCallback(ByVal hwnd As Integer, ByRef lpVHdr As VIDEOHDR) As Boolean
        Debug.Print("Here!")
        Return True
    End Function

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim lngP As Integer
        lngP = SendVideoStreamCallbackMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, 0, AddressOf HandleVideoStreamCallback)
        Debug.Print(lngP)
    End Sub

回调HandleVideoStreamCallback没有任何反应

[水晶烟灰缸]

怎么没人理我啊

[ruanwei1987]

[cosmo_sei]

这个API没用过，我甚至不知道其存在。
帮你顶一下吧。

没反应应该是回调方法没被调用，为何没被调用得看API的运行逻辑了。

[cosmo_sei]

查了API资料回来仔细一看原来是SendMessageA （不就是SendMessage吗？），我以为SendVideoStreamCallbackMessage...

不过，依然无法解答，sorry