Registro para notificação de dispositivo
O sistema operacional pode enviar mensagens de notificação que representam os eventos gerados por um dispositivo. O sistema envia essas notificações para uma janela ou para um serviço do Windows. E você pode se registrar para receber essas notificações chamando a função RegisterDeviceNotification.
Este tópico fornece um exemplo de código que mostra como se registrar para notificações de dispositivo. Você pode identificar o dispositivo sobre o qual receber notificações especificando uma classe de dispositivo ao chamar RegisterDeviceNotification. E você identifica essa classe de dispositivo por seu GUID.
Listagem do código-fonte
Se você quiser criar e executar este exemplo de código-fonte como um aplicativo, comece criando um novo projeto no Microsoft Visual Studio. Crie um novo projeto com base no modelo de projeto Aplicativo da Área de Trabalho do Windows. Nomeie o projeto como RegisterDeviceNotification.
Abra RegisterDeviceNotification.cpp, exclua todo o seu conteúdo e cole na lista abaixo.
// RegisterDeviceNotification.cpp
#include <windows.h>
#include <stdio.h>
#include <tchar.h>
#include <strsafe.h>
#include <dbt.h>
// This GUID is for all USB serial host PnP drivers, but you can replace it
// with any valid device class guid.
GUID WceusbshGUID = { 0x25dbce51, 0x6c8f, 0x4a72,
0x8a,0x6d,0xb5,0x4c,0x2b,0x4f,0xc8,0x35 };
// For informational messages and window titles.
PWSTR g_pszAppName;
void OutputMessage(
HWND hOutWnd,
WPARAM wParam,
LPARAM lParam
)
// Routine Description:
// Support routine.
// Send text to the output window, scrolling if necessary.
// Parameters:
// hOutWnd - Handle to the output window.
// wParam - Standard windows message code, not used.
// lParam - String message to send to the window.
// Return Value:
// None
// Note:
// This routine assumes the output window is an edit control
// with vertical scrolling enabled.
// This routine has no error-checking.
{
LRESULT lResult;
LONG bufferLen;
LONG numLines;
LONG firstVis;
// Make writable and turn off redraw.
lResult = SendMessage(hOutWnd, EM_SETREADONLY, FALSE, 0L);
lResult = SendMessage(hOutWnd, WM_SETREDRAW, FALSE, 0L);
// Obtain current text length in the window.
bufferLen = SendMessage(hOutWnd, WM_GETTEXTLENGTH, 0, 0L);
numLines = SendMessage(hOutWnd, EM_GETLINECOUNT, 0, 0L);
firstVis = SendMessage(hOutWnd, EM_GETFIRSTVISIBLELINE, 0, 0L);
lResult = SendMessage(hOutWnd, EM_SETSEL, bufferLen, bufferLen);
// Write the new text.
lResult = SendMessage(hOutWnd, EM_REPLACESEL, 0, lParam);
// See whether scrolling is necessary.
if (numLines > (firstVis + 1))
{
int lineLen = 0;
int lineCount = 0;
int charPos;
// Find the last nonblank line.
numLines--;
while (!lineLen)
{
charPos = SendMessage(
hOutWnd, EM_LINEINDEX, (WPARAM)numLines, 0L);
lineLen = SendMessage(
hOutWnd, EM_LINELENGTH, charPos, 0L);
if (!lineLen)
numLines--;
}
// Prevent negative value finding min.
lineCount = numLines - firstVis;
lineCount = (lineCount >= 0) ? lineCount : 0;
// Scroll the window.
lResult = SendMessage(
hOutWnd, EM_LINESCROLL, 0, (LPARAM)lineCount);
}
// Done, make read-only and allow redraw.
lResult = SendMessage(hOutWnd, WM_SETREDRAW, TRUE, 0L);
lResult = SendMessage(hOutWnd, EM_SETREADONLY, TRUE, 0L);
}
void ErrorHandler(
LPCTSTR lpszFunction
)
// Routine Description:
// Support routine.
// Retrieve the system error message for the last-error code
// and pop a modal alert box with usable info.
// Parameters:
// lpszFunction - String containing the function name where
// the error occurred plus any other relevant data you'd
// like to appear in the output.
// Return Value:
// None
// Note:
// This routine is independent of the other windowing routines
// in this application and can be used in a regular console
// application without modification.
{
LPVOID lpMsgBuf;
LPVOID lpDisplayBuf;
DWORD dw = GetLastError();
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dw,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR)&lpMsgBuf,
0, NULL);
// Display the error message and exit the process.
lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT,
(lstrlen((LPCTSTR)lpMsgBuf)
+ lstrlen((LPCTSTR)lpszFunction) + 40)
* sizeof(TCHAR));
if (!lpDisplayBuf) return;
StringCchPrintf((LPTSTR)lpDisplayBuf,
LocalSize(lpDisplayBuf) / sizeof(TCHAR),
TEXT("%s failed with error %d: %s"),
lpszFunction, dw, (LPCTSTR)lpMsgBuf);
MessageBox(NULL, (LPCTSTR)lpDisplayBuf, g_pszAppName, MB_OK);
LocalFree(lpMsgBuf);
LocalFree(lpDisplayBuf);
}
BOOL DoRegisterDeviceInterfaceToHwnd(
IN GUID InterfaceClassGuid,
IN HWND hWnd,
OUT HDEVNOTIFY* hDeviceNotify
)
// Routine Description:
// Registers an HWND for notification of changes in the device interfaces
// for the specified interface class GUID.
// Parameters:
// InterfaceClassGuid - The interface class GUID for the device
// interfaces.
// hWnd - Window handle to receive notifications.
// hDeviceNotify - Receives the device notification handle. On failure,
// this value is NULL.
// Return Value:
// If the function succeeds, the return value is TRUE.
// If the function fails, the return value is FALSE.
// Note:
// RegisterDeviceNotification also allows a service handle be used,
// so a similar wrapper function to this one supporting that scenario
// could be made from this template.
{
DEV_BROADCAST_DEVICEINTERFACE NotificationFilter;
ZeroMemory(&NotificationFilter, sizeof(NotificationFilter));
NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
NotificationFilter.dbcc_classguid = InterfaceClassGuid;
*hDeviceNotify = RegisterDeviceNotification(
hWnd, // events recipient
&NotificationFilter, // type of device
DEVICE_NOTIFY_WINDOW_HANDLE // type of recipient handle
);
if (NULL == *hDeviceNotify)
{
ErrorHandler(L"RegisterDeviceNotification");
return FALSE;
}
return TRUE;
}
void MessagePump(
HWND hWnd
)
// Routine Description:
// Simple main thread message pump.
//
// Parameters:
// hWnd - handle to the window whose messages are being dispatched
// Return Value:
// None.
{
MSG msg;
int retVal;
// Get all messages for any window that belongs to this thread,
// without any filtering. Potential optimization could be
// obtained via use of filter values if desired.
while ((retVal = GetMessage(&msg, NULL, 0, 0)) != 0)
{
if (retVal == -1)
{
ErrorHandler(L"GetMessage");
break;
}
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
}
INT_PTR WINAPI WinProcCallback(
HWND hWnd,
UINT message,
WPARAM wParam,
LPARAM lParam
)
// Routine Description:
// Simple Windows callback for handling messages.
// This is where all the work is done because the example
// is using a window to process messages. This logic would be handled
// differently if registering a service instead of a window.
// Parameters:
// hWnd - the window handle being registered for events.
// message - the message being interpreted.
// wParam and lParam - extended information provided to this
// callback by the message sender.
// For more information regarding these parameters and return value,
// see the documentation for WNDCLASSEX and CreateWindowEx.
{
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(L"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.
ErrorHandler(L"CreateWindow: Edit Control");
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.
//
PDEV_BROADCAST_DEVICEINTERFACE b = (PDEV_BROADCAST_DEVICEINTERFACE)lParam;
TCHAR strBuff[256];
// Output some messages to the window.
switch (wParam)
{
case DBT_DEVICEARRIVAL:
msgCount++;
StringCchPrintf(
strBuff, 256,
TEXT("Message %d: DBT_DEVICEARRIVAL\n"), (int)msgCount);
break;
case DBT_DEVICEREMOVECOMPLETE:
msgCount++;
StringCchPrintf(
strBuff, 256,
TEXT("Message %d: DBT_DEVICEREMOVECOMPLETE\n"), (int)msgCount);
break;
case DBT_DEVNODES_CHANGED:
msgCount++;
StringCchPrintf(
strBuff, 256,
TEXT("Message %d: DBT_DEVNODES_CHANGED\n"), (int)msgCount);
break;
default:
msgCount++;
StringCchPrintf(
strBuff, 256,
TEXT("Message %d: WM_DEVICECHANGE message received, value %d unhandled.\n"),
(int)msgCount, wParam);
break;
}
OutputMessage(hEditWnd, wParam, (LPARAM)strBuff);
}
break;
case WM_CLOSE:
if (!UnregisterDeviceNotification(hDeviceNotify))
{
ErrorHandler(L"UnregisterDeviceNotification");
}
DestroyWindow(hWnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
// Send all other messages on to the default windows handler.
lRet = DefWindowProc(hWnd, message, wParam, lParam);
break;
}
return lRet;
}
#define WND_CLASS_NAME TEXT("SampleAppWindowClass")
BOOL InitWindowClass()
// Routine Description:
// Simple wrapper to initialize and register a window class.
// Parameters:
// None
// Return Value:
// TRUE on success, FALSE on failure.
// Note:
// wndClass.lpfnWndProc and wndClass.lpszClassName are the
// important unique values used with CreateWindowEx and the
// Windows message pump.
{
WNDCLASSEX wndClass;
wndClass.cbSize = sizeof(WNDCLASSEX);
wndClass.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW;
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 = CreateSolidBrush(RGB(192, 192, 192));
wndClass.hCursor = LoadCursor(0, IDC_ARROW);
wndClass.lpszClassName = WND_CLASS_NAME;
wndClass.lpszMenuName = NULL;
wndClass.hIconSm = wndClass.hIcon;
if (!RegisterClassEx(&wndClass))
{
ErrorHandler(L"RegisterClassEx");
return FALSE;
}
return TRUE;
}
int __stdcall _tWinMain(
_In_ HINSTANCE hInstanceExe,
_In_opt_ HINSTANCE, // should not reference this parameter
_In_ PTSTR lpstrCmdLine,
_In_ int nCmdShow)
{
//
// To enable a console project to compile this code, set
// Project->Properties->Linker->System->Subsystem: Windows.
//
int nArgC = 0;
PWSTR* ppArgV = CommandLineToArgvW(lpstrCmdLine, &nArgC);
g_pszAppName = ppArgV[0];
if (!InitWindowClass())
{
// InitWindowClass displays any errors
return -1;
}
// Main app window
HWND hWnd = CreateWindowEx(
WS_EX_CLIENTEDGE | WS_EX_APPWINDOW,
WND_CLASS_NAME,
g_pszAppName,
WS_OVERLAPPEDWINDOW, // style
CW_USEDEFAULT, 0,
640, 480,
NULL, NULL,
hInstanceExe,
NULL);
if (hWnd == NULL)
{
ErrorHandler(L"CreateWindowEx: main appwindow hWnd");
return -1;
}
// Actually draw the window.
ShowWindow(hWnd, SW_SHOWNORMAL);
UpdateWindow(hWnd);
// The message pump loops until the window is destroyed.
MessagePump(hWnd);
return 1;
}
Agora você poderá compilar e executar o projeto.
Sobre o exemplo de código
O exemplo de código usa um identificador de janela para notificações de alteração de dispositivo e contém uma grande quantidade de código apenas para gerenciar a infraestrutura de janelas. Um aplicativo destinado a ser instalado como um serviço do Windows conteria código de infraestrutura diferente.
O aplicativo receberá a mensagem WM_DEVICECHANGE sempre que uma notificação de evento da interface do dispositivo USB for enviada.
O sistema transmite um conjunto de eventos de alteração de dispositivo padrão para todos os aplicativos e serviços. Você não precisa se registrar para receber esses eventos padrão. Para obter detalhes, consulte a seção Comentários em RegisterDeviceNotification.