Thread Subject: how to get the camera handler in image acquisition toolbox adaptor?

I am working on the development of a customised image acquisition toolboc adaptor. I have device's SDK(uEye camera SDK). Any image acquisition starts from getting the camera handler by the function:
       HIDS m_hCam = (HIDS) 0;
       is_InitCamera(&m_hCam, m_hWndDisplay);
,where m_hCam is the type of "void *". If there is only one camera linking to the computer, Matlab will crash when typing command "preview". But, if I have two cameras connected, then it is fine.

So, I guess the first camera is being locked by the adaptor itself. I fail to gain the access to the default camera. How do I get the camera handler from the adaptor and pass to m_hCam? I read the toolbox user's guide but there is little information on this topic.

Many tks for comments.