请教：VB连接摄像头，第一次正常后，再打开就总是弹出一个视频源界面。

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Private Declare Function capCreateCaptureWindow Lib "avicap32.dll" Alias "capCreateCaptureWindowA" (ByVal lpszWindowName As String, ByVal dwStyle As Long, ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hwndParent As Long, ByVal nID As Long) As Long

Dim GetPicture As Long

Dim nStyle As Long

Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

'视频窗口控制消息常数

Const WS_Child = &H40000000: Const WS_Visible = &H10000000

Const WS_Caption = &HC00000: Const WS_ThickFrame = &H40000

Const WM_User = &H400                       '用户消息开始号

Const WM_CAP_Connect = WM_User + 10         '连接一个摄像头

Const WM_CAP_DisConnect = WM_User + 11      '断开一个摄像头的连接

Const WM_CAP_Set_PreView = WM_User + 50     '使预览模式有效或者失效

Const WM_CAP_Set_Overlay = WM_User + 51     '使窗口处于叠加模式，也会自动地使预览模式失效。

Const WM_CAP_Set_PreViewRate = WM_User + 52 '设置在预览模式下帧的显示频率

Const WM_CAP_Edit_Copy = WM_User + 30       '将当前图像复制到剪贴板

Const WM_CAP_Sequence = WM_User + 62        '开始录像，录像未结束前不会返回。

Const WM_Cap_File_Set_File = WM_User + 20   '设置当前的视频捕捉文件

Const WM_Cap_File_Get_File = WM_User + 21   '得到当前的视频捕捉文件

Private Const WM_CLOSE = &H10

.......

.......

GetPicture = WS_Child + WS_Visible

nStyle = capCreateCaptureWindow("", GetPicture, 1, 78, 640, 400, Me.hwnd, 0)

SendMessage nStyle, WM_CAP_Connect, 0, 0 '连接摄像头

.......

SendMessage nStyle, WM_CAP_DisConnect, 0, 0  ‘断开摄像头

SendMessage nStyle, WM_CLOSE, 0, 0