谁能告诉我为什么在使用以下代码时我收到多个(三个或四个设备到达通知)?
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
Const WM_DEVICECHANGE As Integer = &H219
Const DBT_DEVICEARRIVAL As Integer = &H8000
Const DBT_DEVICEREMOVECOMPLETE As Integer = &H8004
If m.Msg = WM_DEVICECHANGE Then
If m.WParam.ToInt32() = DBT_DEVICEARRIVAL then
messagebox.show("Device arrived")
ElseIf m.WParam.ToInt32 = DBT_DEVICEREMOVECOMPLETE And valid = True Then
messagebox.show("device left")
End If
End If
MyBase.WndProc(m)
End Sub
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Public Structure DEV_BROADCAST_DEVICEINTERFACE
Public dbcc_size As Integer
Public dbcc_devicetype As Integer
Public dbcc_reserved As Integer
<MarshalAs(UnmanagedType.ByValArray, ArraySubType:=UnmanagedType.U1, SizeConst:=16)> _
Public dbcc_classguid As Byte()
<MarshalAs(UnmanagedType.ByValArray, SizeConst:=128)> _
Public dbcc_name As Char()
End Structure
Public Sub RegisterDeviceNotification()
Dim usb_id As String = "745dd1a8-fca4-4659-9df2-954176705158"
Dim deviceInterface As New DEV_BROADCAST_DEVICEINTERFACE()
Dim size As Integer = Marshal.SizeOf(deviceInterface)
deviceInterface.dbcc_size = size
deviceInterface.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE
deviceInterface.dbcc_reserved = 0
deviceInterface.dbcc_classguid = New Guid(usb_id).ToByteArray
Dim buffer As IntPtr = Nothing
buffer = Marshal.AllocHGlobal(size)
Marshal.StructureToPtr(deviceInterface, buffer, True)
rPS4000 = RegisterDeviceNotification(Me.Handle, buffer, _
DEVICE_NOTIFY_WINDOW_HANDLE Or _
DEVICE_NOTIFY_ALL_INTERFACE_CLASSES)
End Sub
当设备到达时,我希望启动一个线程来检测哪些设备连接到我的机器。如果新设备是我感兴趣的特定硬件(示波器),那么我想使用相应的驱动程序连接到该设备。我遇到的问题是我收到多个 DBT_DEVICEARRIVAL 通知,因此当我的设备被插入时,我的软件会尝试多次连接它——我只希望这种情况发生一次。我有一个使用计时器来解决这个问题的方法,但我想知道是否有某种方法可以只接收一个 DBT_DEVICEARRIVAL 通知。
谢谢