Обнаружить, подключено ли USB-устройство или отключено?

Code:

unit U_Usb;

interface

uses

Windows, Messages, SysUtils, Classes, Forms;

type

PDevBroadcastHdr  = ^DEV_BROADCAST_HDR;

DEV_BROADCAST_HDR = packed record

   dbch_size: DWORD;

   dbch_devicetype: DWORD;

   dbch_reserved: DWORD;

end;

PDevBroadcastDeviceInterface  = ^DEV_BROADCAST_DEVICEINTERFACE;

DEV_BROADCAST_DEVICEINTERFACE = record

   dbcc_size: DWORD;

   dbcc_devicetype: DWORD;

   dbcc_reserved: DWORD;

   dbcc_classguid: TGUID;

   dbcc_name: short;

end;

const

GUID_DEVINTERFACE_USB_DEVICE: TGUID = '{A5DCBF10-6530-11D2-901F-00C04FB951ED}';

DBT_DEVICEARRIVAL          = $8000;          // system detected a new device

DBT_DEVICEREMOVECOMPLETE   = $8004;          // device is gone

DBT_DEVTYP_DEVICEINTERFACE = $00000005;      // device interface class

type

TComponentUSB = class(TComponent)

private

   FWindowHandle: HWND;

   FOnUSBArrival: TNotifyEvent;

   FOnUSBRemove: TNotifyEvent;

   procedure WndProc(var Msg: TMessage);

   function USBRegister: Boolean;

protected

   procedure WMDeviceChange(var Msg: TMessage); dynamic;

public

   constructor Create(AOwner: TComponent); override;

   destructor Destroy; override;

published

   property OnUSBArrival: TNotifyEvent read FOnUSBArrival write FOnUSBArrival;

   property OnUSBRemove: TNotifyEvent read FOnUSBRemove write FOnUSBRemove;

end;

implementation

constructor TComponentUSB.Create(AOwner: TComponent);

begin

inherited Create(AOwner);

FWindowHandle := AllocateHWnd(WndProc);

USBRegister;

end;

destructor TComponentUSB.Destroy;

begin

DeallocateHWnd(FWindowHandle);

inherited Destroy;

end;

procedure TComponentUSB.WndProc(var Msg: TMessage);

begin

if (Msg.Msg = WM_DEVICECHANGE) then

begin

   try

     WMDeviceChange(Msg);

   except

     Application.HandleException(Self);

   end;

end

else

   Msg.Result := DefWindowProc(FWindowHandle, Msg.Msg, Msg.wParam, Msg.lParam);

end;

procedure TComponentUSB.WMDeviceChange(var Msg: TMessage);

var

devType: Integer;

Datos: PDevBroadcastHdr;

begin

if (Msg.wParam = DBT_DEVICEARRIVAL) or (Msg.wParam = DBT_DEVICEREMOVECOMPLETE) then

begin

   Datos := PDevBroadcastHdr(Msg.lParam);

   devType := Datos^.dbch_devicetype;

   if devType = DBT_DEVTYP_DEVICEINTERFACE then

   begin // USB Device

     if Msg.wParam = DBT_DEVICEARRIVAL then

     begin

       if Assigned(FOnUSBArrival) then

         FOnUSBArrival(Self);

     end

     else

     begin

       if Assigned(FOnUSBRemove) then

         FOnUSBRemove(Self);

     end;

   end;

end;

end;

function TComponentUSB.USBRegister: Boolean;

var

dbi: DEV_BROADCAST_DEVICEINTERFACE;

Size: Integer;

r: Pointer;

begin

Result := False;

Size := SizeOf(DEV_BROADCAST_DEVICEINTERFACE);

ZeroMemory(@dbi, Size);

dbi.dbcc_size := Size;

dbi.dbcc_devicetype := DBT_DEVTYP_DEVICEINTERFACE;

dbi.dbcc_reserved := 0;

dbi.dbcc_classguid  := GUID_DEVINTERFACE_USB_DEVICE;

dbi.dbcc_name := 0;

r := RegisterDeviceNotification(FWindowHandle, @dbi,

   DEVICE_NOTIFY_WINDOW_HANDLE

   );

if Assigned(r) then Result := True;

end;

end.