// Component to detect when usb devices are connected or disconnected
// using RegisterDeviceNotification
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;
procedure Register;
begin
RegisterComponents('
ComponentUSB',[TComponentUSB]);
end;
end.