注册设备通知
操作系统可以发送表示设备引发事件的通知消息。 系统将这些通知发送到窗口或 Windows 服务。 可以通过调用 RegisterDeviceNotification 函数来注册，以接收这些通知。
本主题提供了一个代码示例，演示如何注册设备通知。 调用 RegisterDeviceNotification 时，可以通过指定设备类来标识要接收通知的设备。 可通过 GUID 标识该设备类。
源代码列表
如果要生成并运行此源代码示例作为应用，请首先在 Microsoft Visual Studio 中创建新项目。 根据 Windows 桌面应用程序 项目模板创建新项目。 将项目命名为 RegisterDeviceNotification。
打开 RegisterDeviceNotification.cpp，删除其整个内容，然后粘贴以下列表。
// 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;
}
现在可以生成并运行该项目了。
关于代码示例
该代码示例对设备更改通知使用窗口句柄，并且它包含大量代码，只是为了管理开窗基础结构。 要作为 Windows 服务安装的应用程序将包含不同的基础结构代码。
每当发送 USB 设备接口事件通知时，应用程序都会收到 WM_DEVICECHANGE 消息。
系统将一组默认设备更改事件广播到所有应用程序和服务。 无需注册即可接收这些默认事件。 有关详细信息，请参阅 RegisterDeviceNotification 中的备注部分。