在WINCE系統中,可以通過由窗口接收一個事件來判斷有新設備插入。
窗口只需要接收該消息:WM_DEVICECHANGE。然後,通過判斷設備類型和設備名稱就可以判斷具體的設備插入。
例如判斷 SD卡的插入和拔出操作,其中SD卡的設備名爲"DSK1:",那麼可以在頂層窗口中接收並判斷此消息:
case WM_DEVICECHANGE:
{
DEV_BROADCAST_HDR* dhr = (DEV_BROADCAST_HDR *)lParam;
PDEV_BROADCAST_PORT lpdbp = (PDEV_BROADCAST_PORT)dhr;
if( DBT_DEVTYP_PORT == lpdbp->dbcp_devicetype && !wcsicmp(lpdbp->dbcp_name, L"DSK1:")) {
switch(wParam) {
case DBT_DEVICEARRIVAL: //SD卡插入
m_Flag_SD_Detected = TRUE;
break;
case DBT_DEVICEREMOVECOMPLETE://SD卡拔出
m_Flag_SD_Detected = FALSE;
break;
}
}
}
當然了,這個消息的發送也是要驅動程序去實現的。一般在驅動程序中有對設備在線和離線狀態的判斷,一旦發現狀態有變,就會廣播一個消息,也可以只往某個窗口發送消息。以下是USB從機驅動判斷插入和拔出的廣播消息的實現:
static VOID BroadcastUSBINSERT(
LPTSTR DevName,
BOOL bNew
)
{
PDEV_BROADCAST_PORT pBCast;
DWORD len;
LPTSTR str;
static DWORD insert_times = 0; //記錄USB插入的次數
if(bNew == TRUE){
insert_times++;
}else if(insert_times <= 0){
return;
}else{
insert_times = 0;
}
len = sizeof(DEV_BROADCAST_HDR) + (_tcslen(DevName) + 1)*sizeof(TCHAR);
pBCast = (PDEV_BROADCAST_PORT)LocalAlloc(LPTR, len);
if (pBCast == NULL) {
return;
}
pBCast->dbcp_devicetype = DBT_DEVTYP_PORT;
pBCast->dbcp_reserved = 0;
str = (LPTSTR)&(pBCast->dbcp_name[0]);
_tcscpy(str, DevName);
pBCast->dbcp_size = len;
DEBUGMSG(ZONE_PNP,
(TEXT("DEVICE!BroadcastDeviceChange Calling SendNotifyMessage for device %s\r\n"), DevName));
NKDbgPrintfW((TEXT("Sendmsg : %s\r\n")),(bNew)?TEXT("enter"):TEXT("exit"));
// Call the function
SendNotifyMessage(
HWND_BROADCAST,
WM_DEVICECHANGE,
(bNew) ? DBT_DEVICEARRIVAL : DBT_DEVICEREMOVECOMPLETE,
(LPARAM)pBCast);
LocalFree(pBCast);
}
這樣,用剛開始的辦法,在窗口中接收WM_DEVICECHANGE消息就可以進行異步判斷USB設備插入和拔出的動作了。