vc弹出USB的方法. 附试验通过的代码
bool CUsbSwitchDlg::UnInstallUsb(char szDriveName) //参数是要弹出的盘符如：G，F{ DWORD accessMode = 0, shareMode = 0; HANDLE hDevice; ULONG returned = 0,bResult = 0; DWORD dwError; shareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;// default accessMode = GENERIC_WRITE | GENERIC_READ; // default if (szDriveName == 0) { return FALSE; } CString vol_string = \\\\.\\G:; vol_string.SetAt(4, szDriveName); hDevice = CreateFile(vol_string, accessMode, shareMode, NULL, OPEN_EXISTING, 0, NULL); if (hDevice == INVALID_HANDLE_VALUE) { CString debugInfo; dwError = GetLastError(); debugInfo.Format("error = %d ", dwError); TRACE("IOCTL_STORAGE_EJECT_MEDIAerrorcode = %d \n", dwError); return FALSE; } bResult = DeviceIoControl(hDevice, IOCTL_STORAGE_EJECT_MEDIA, //弹出U盘的具体命令。 NULL, 0, NULL, 0,&returned, NULL); if (!bResult) // IOCTL failed //经实验，有时虽然失败了，U盘还是能弹出 { CString debugInfo; dwError = GetLastError(); debugInfo.Format("error = %d ", dwError); TRACE("IOCTL_STORAGE_EJECT_MEDIAerrorcode = %d \n", dwError); } bResult = CloseHandle(hDevice); if (!bResult) { CString debugInfo; dwError = GetLastError(); debugInfo.Format("error = %d ", dwError); TRACE("IOCTL_STORAGE_EJECT_MEDIAerrorcode = %d \n", dwError); return FALSE; } return TRUE;} 关于U盘盘符的问题：
添加WM_DEVICECHANGE的消息处理函数OnDeviceChange,在该函数中捕获DBT_DEVICEARRIVAL事件(当U盘插入时,OS会发WM_DEVICECHANGE广播消息,该消息的wParam中会包含DBT_DEVICEARRIVAL事件),同时得到DEV_BROADCAST_VOLUME结构的数据,DEV_BROADCAST_VOLUME结构的dbch_devicetype 成员是DBT_DEVTYP_VOLUME代表是磁盘。dbcv_unitmask成员是一个Mask变量,最低位对应A,其次是B,...,根据它可就可以得到当前U盘的盘符了. 比如0x1代表A盘。0x10代表B盘。当然同理你可以得到系统上刚插入的串口设备。要学会举一反三。
BOOL CUsbSwitchDlg::OnDeviceChange( UINT nEventType, DWORD dwData ){ if (nEventType == DBT_DEVICEARRIVAL) { DEV_BROADCAST_HDR* dev_hdr = (DEV_BROADCAST_HDR*)dwData; if (dev_hdr->dbch_devicetype == DBT_DEVTYP_VOLUME) { DEV_BROADCAST_VOLUME* pdev_vol = (DEV_BROADCAST_VOLUME*)dwData;; int vol_char = 0; int vol_int = pdev_vol->dbcv_unitmask; // calculate the vol_num for (;vol_int;) { vol_int = vol_int/2; vol_char++; } m_USBvolNum = vol_char + 'A' - 1;//m_USBvolNum即为盘符，如G或者I
} } return FALSE;}
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