Recently I needed to determine when removable media, such as a zip disk or
media card, had been inserted by the user.
I initially looked into the WM_DEVICECHANGE broadcast message
only to realise this supports CDROMs and little else. Fortunately there is
another way via the shell, through the scarcely documented
SHChangeNotifyRegister function.
We can register to be informed by the shell when certain events of interest
occur. The events are numerous - covering when a drive is added or removed,
files are renamed, etc. However of particular interest here are the
notifications for media being inserted or removed.
Its scarcely rocket science but piecing the various bits of information
together to utilise this functionality took far longer than it should. I was
amazed there was no article here on CP covering this, so figured I should
rectify that!
ImplementationYou will need the following includes and definition:#include <shlobj.h> #define WM_USER_MEDIACHANGED WM_USER+88 Together
with a member variable to release the request later:ULONG m_ulSHChangeNotifyRegister; Nullify the member variable in your
constructor, then register to be notified by the shell (perhaps in OnInitDialog
for example):
CMyWnd::CMyWnd() { ulSHChangeNotifyRegister = NULL; }
BOOL CMyWnd::OnInitDialog() { CWnd::OnInitDialog();
HWND hWnd = GetSafeHwnd(); LPITEMIDLIST ppidl; if(SHGetSpecialFolderLocation(hWnd, CSIDL_DESKTOP, &ppidl) == NOERROR) { SHChangeNotifyEntry shCNE; shCNE.pidl = ppidl; shCNE.fRecursive = TRUE;
m_ulSHChangeNotifyRegister = SHChangeNotifyRegister(hWnd, SHCNE_DISKEVENTS, SHCNE_MEDIAINSERTED|SHCNE_MEDIAREMOVED, WM_USER_MEDIACHANGED, 1, &shCNE); ASSERT(m_ulSHChangeNotifyRegister != 0); } else ASSERT(FALSE); } Add a message handler to your message map for the notification message:ON_MESSAGE(WM_USER_MEDIACHANGED, OnMediaChanged) Together with the
corresponding declaration:afx_msg LRESULT OnMediaChanged(WPARAM, LPARAM); Then deal with the
message as desired:
typedef struct { DWORD dwItem1; DWORD dwItem2; } SHNOTIFYSTRUCT;
LRESULT CMyWnd::OnMediaChanged(WPARAM wParam, LPARAM lParam) { SHNOTIFYSTRUCT *shns = (SHNOTIFYSTRUCT *)wParam; CString strPath, strMsg;
switch(lParam) { case SHCNE_MEDIAINSERTED: { strPath = GetPathFromPIDL(shns->dwItem1); if(!strPath.IsEmpty()) { strMsg.Format("Media inserted into %s", strPath); AfxMessageBox(strMsg); } } case SHCNE_MEDIAREMOVED: { strPath = GetPathFromPIDL(shns->dwItem1); if(!strPath.IsEmpty()) { strMsg.Format("Media removed from %s", strPath); AfxMessageBox(strMsg); } } } return NULL; }
CString CMyWnd::GetPathFromPIDL(DWORD pidl) { char sPath[MAX_PATH]; CString strTemp = _T(""); if(SHGetPathFromIDList((struct _ITEMIDLIST *)pidl, sPath)) strTemp = sPath; return strTemp; }
Finally deregister your request when no longer required:void CMyWnd::OnDestroy() { if(m_ulSHChangeNotifyRegister) VERIFY(SHChangeNotifyDeregister(m_ulSHChangeNotifyRegister));
CWnd::OnDestroy(); }
Tags: C++ CAsyncSocket Removable Disk Detection Removable Media Detection SHCNE_DISKEVENTS SHCNE_MEDIAINESERTED SHChangeNotifyRegister SHNE_MEDIAREMOVED WM_DEVICECHANGE WM_USER_MEDIACHANGED
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