【发布时间】：2015-03-11 22:30:44
【问题描述】：
我一直致力于检测 USB 插入/移除。我已经使用 CreateWindowEx() 实现了代码，通过我的窗口进程回调传递了一个 WNCLASSEX。在插入和移除我的 USB 时，我成功收到 WM_DEVICECHANGE 消息，但 wParam 始终设置为 DBT_DEVNODES_CHANGED。
我从来没有得到 DBT_DEVICEARRIVAL 或 DBT_DEVICEREMOVECOMPLETE。我一直在使用我得到的东西，但我真的需要能够区分设备到达和移除之间的区别，以便我可以根据收到的内容采取不同的操作。
现在，我必须在收到 DBT_DEVNODES_CHANGED 后设置一个计时器，然后测试系统上是否有任何新的可移动设备，或者我的列表中是否不再有任何可移动设备。我确定这是不对的，所以我想我会问。我宁愿摆脱计时器，只接收这两条消息。这对我必须做的事情有很大帮助。有什么建议吗？
这是我注册回调的代码，以及回调本身：
注意：2015 年 3 月 12 日：更新代码以显示实际 GUID 和 DoRegisterDeviceInterfaceToHwnd() 函数的定义。）：
GUID WceusbshGUID = { 0x25dbce51, 0x6c8f, 0x4a72, 0x8a,0x6d,0xb5,0x4c,0x2b,0x4f,0xc8,0x35 };
//GUID WusbrawGUID = {0xa5dcbf10, 0x6530, 0x11d2, 0x90, 0x1f, 0x00, 0xc0, 0x4f, 0xb9, 0x51, 0xed };
//GUID WusbGUID = {0x88BAE032, 0x5A81, 0x49f0, 0xBC, 0x3D, 0xA4, 0xFF, 0x13, 0x82, 0x16, 0xD6 };
INT_PTR WINAPI WinProcCallback(HWND __hWnd, UINT message, WPARAM wParam, LPARAM lParam);
BOOL DoRegisterDeviceInterfaceToHwnd(GUID InterfaceClassGuid, HWND __hWnd, HDEVNOTIFY *hDeviceNotify);
bool UsbController::startNotifyUsbAddedRemoved(QString &errmsg)
{
WNDCLASSEX wndClass;
wndClass.cbSize = sizeof(wndClass);
wndClass.style = 0;
wndClass.hInstance = reinterpret_cast<HINSTANCE>(GetModuleHandle(0));
wndClass.lpfnWndProc = reinterpret_cast<WNDPROC>(WinProcCallback);
wndClass.cbClsExtra = 0;
wndClass.cbWndExtra = 0;
wndClass.hIcon = LoadIcon(0, IDI_APPLICATION);
wndClass.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wndClass.hCursor = LoadCursor(0, IDC_ARROW);
wndClass.lpszClassName = WND_CLASS_NAME;
wndClass.lpszMenuName = NULL;
wndClass.hIconSm = LoadIcon(0, IDI_APPLICATION);
if (!RegisterClassEx(&wndClass))
{
FormatErrorMsg("RegisterClassEx: ", errmsg);
return false;
}
HINSTANCE hInstance = (HINSTANCE)::GetModuleHandle(NULL);
__hWnd = CreateWindowEx(
WS_EX_CLIENTEDGE | WS_EX_APPWINDOW,
WND_CLASS_NAME,
WND_APP_NAME,
WS_OVERLAPPEDWINDOW, // style
CW_USEDEFAULT, 0,
0, 0,
NULL, NULL,
hInstance,
NULL);
if ( __hWnd == NULL )
{
FormatErrorMsg("CreateWindowEx: ", errmsg);
return false;
}
return true;
}
INT_PTR WINAPI WinProcCallback(HWND __hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
LRESULT lRet = 1;
static HDEVNOTIFY hDeviceNotify;
static HWND hEditWnd;
static ULONGLONG msgCount = 0;
switch (message)
{
case WM_CREATE:
//
// This is the actual registration., In this example, registration
// should happen only once, at application startup when the window
// is created.
//
// If you were using a service, you would put this in your main code
// path as part of your service initialization.
//
if ( ! DoRegisterDeviceInterfaceToHwnd( WceusbshGUID, __hWnd, &hDeviceNotify) )
{
// Terminate on failure.
//ErrorHandler(TEXT("DoRegisterDeviceInterfaceToHwnd"));
ExitProcess(1);
}
//
// Make the child window for output.
//
hEditWnd = CreateWindow(TEXT("EDIT"),// predefined class
NULL, // no window title
WS_CHILD | WS_VISIBLE | WS_VSCROLL |
ES_LEFT | ES_MULTILINE | ES_AUTOVSCROLL,
0, 0, 0, 0, // set size in WM_SIZE message
__hWnd, // parent window
(HMENU)1, // edit control ID
(HINSTANCE) GetWindowLong(__hWnd, GWL_HINSTANCE),
NULL); // pointer not needed
if ( hEditWnd == NULL )
{
// Terminate on failure.
ExitProcess(1);
}
// Add text to the window.
SendMessage(hEditWnd, WM_SETTEXT, 0,
(LPARAM)TEXT("Registered for USB device notification...\n"));
break;
case WM_SETFOCUS:
SetFocus(hEditWnd);
break;
case WM_SIZE:
// Make the edit control the size of the window's client area.
MoveWindow(hEditWnd,
0, 0, // starting x- and y-coordinates
LOWORD(lParam), // width of client area
HIWORD(lParam), // height of client area
TRUE); // repaint window
break;
case WM_DEVICECHANGE:
{
//
// This is the actual message from the interface via Windows messaging.
// This code includes some additional decoding for this particular device type
// and some common validation checks.
//
// Note that not all devices utilize these optional parameters in the same
// way. Refer to the extended information for your particular device type
// specified by your GUID.
//
// Output some messages to the window.
UsbController *pusbctl;
switch (wParam)
{
case DBT_DEVICEARRIVAL:
msgCount++;
pusbctl = UsbController::instance();
pusbctl->signalDeviceArrival();
break;
case DBT_DEVICEREMOVECOMPLETE:
msgCount++;
pusbctl = UsbController::instance();
pusbctl->signalDeviceRemoval();
break;
case DBT_DEVNODES_CHANGED:
msgCount++;
pusbctl = UsbController::instance();
pusbctl->signalDeviceAddedRemoved();
break;
default:
msgCount++;
break;
}
}
break;
default:
// Send all other messages on to the default windows handler.
lRet = DefWindowProc(__hWnd, message, wParam, lParam);
break;
}
return lRet;
}
BOOL DoRegisterDeviceInterfaceToHwnd(GUID InterfaceClassGuid, HWND __hWnd, HDEVNOTIFY *hDeviceNotify)
{
DEV_BROADCAST_DEVICEINTERFACE NotificationFilter;
ZeroMemory( &NotificationFilter, sizeof(NotificationFilter) );
NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
//NotificationFilter.dbcc_devicetype = DEVICE_NOTIFY_ALL_INTERFACE_CLASSES;
NotificationFilter.dbcc_classguid = InterfaceClassGuid;
*hDeviceNotify = RegisterDeviceNotification(
__hWnd, // events recipient
&NotificationFilter, // type of device
DEVICE_NOTIFY_WINDOW_HANDLE // type of recipient handle
);
if ( NULL == *hDeviceNotify )
{
return FALSE;
}
return TRUE;
}
【问题讨论】：
-
你看到msdn.microsoft.com/en-us/library/windows/desktop/…了吗？它说您实际上不需要注册即可获得媒体到达通知。我想知道您正在注册这一事实是否会以某种方式干扰。
-
嗯，我的水晶球说你正在按照程序员的方式做这件事，只是在没有通过“安全删除硬件”的情况下猛拉设备。然后希望 Windows 可以猜测可能发生的事情。嗯，它确实告诉了你。
-
实际上，我确实做了“安全删除硬件”过程。我到达那里的通知值为 7，即 DBT_DEVNODES_CHANGED。我从那个操作中收到了许多消息（尚未从插槽中拉出设备），所有这些消息的值都是 7。当然，当我拉出设备时，我得到的值相同。插入设备具有相同的确切结果。我收到了许多消息，所有消息的 DBT_DEVNODES_CHANGED 的值为 7。