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...get notified when a CD is removed or inserted?
Autor: Thomas Stutz
[ Print tip ]  

Tip Rating (36):  
     


{
  Some applications need to know when the user inserts or
  removes a compact disc or DVD from a CD-ROM drive without
  polling for media changes. Windows provide a way to notify these
  applications through the WM_DEVICECHANGE message.
}

type
  
TForm1 = class(TForm)
  private
    procedure 
WMDeviceChange(var Msg: TMessage); message WM_DEVICECHANGE;
  public

  end
;

{...}

implementation

{$R *.DFM}

procedure TForm1.WMDeviceChange(var Msg: TMessage);
const
  
DBT_DEVICEARRIVAL = $8000; // system detected a new device
  
DBT_DEVICEREMOVECOMPLETE = $8004;  // device is gone
var
  
myMsg: string;
begin
  inherited
;
  case Msg.wParam of
    
DBT_DEVICEARRIVAL: myMsg  := 'CD inserted!';
    DBT_DEVICEREMOVECOMPLETE: myMsg := 'CD removed!';
  end;
  ShowMessage(myMsg);
end;


{*********************************************}

// Advanced Code:
// When the device is of type volume, then we can get some device specific
// information, namely specific information about a logical volume.
// by Juergen Kantz

unit Unit1;

interface

uses
  
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  
TForm1 = class(TForm)
    Button1: TButton;
    label1: TLabel;
  private
    procedure 
WMDeviceChange(var Msg: TMessage); message WM_DeviceChange;
    { Private declarations }
  
public
    
{ Public declarations }
  
end;

const  
  
DBT_DeviceArrival = $8000;
  DBT_DeviceRemoveComplete = $8004;
  DBTF_Media = $0001;
  DBT_DevTyp_Volume = $0002;

type
  
PDevBroadcastHdr = ^TDevBroadcastHdr;
  TDevBroadcastHdr = packed record
    
dbcd_size: DWORD;
    dbcd_devicetype: DWORD;
    dbcd_reserved: DWORD;
  end;

type
  
PDevBroadcastVolume = ^TDevBroadcastVolume;
  TDevBroadcastVolume = packed record
    
dbcv_size: DWORD;
    dbcv_devicetype: DWORD;
    dbcv_reserved: DWORD;
    dbcv_unitmask: DWORD;
    dbcv_flags: Word;
  end;

var
  
Form1: TForm1;


implementation

{$R *.dfm}


function GetDrive(pDBVol: PDevBroadcastVolume): string;
var
  
i: Byte;
  Maske: DWORD;
begin
  if 
(pDBVol^.dbcv_flags and DBTF_Media) = DBTF_Media then
  begin
    
Maske := pDBVol^.dbcv_unitmask;
    for i := 0 to 25 do
    begin
      if 
(Maske and 1) = 1 then
        
Result := Char(i + Ord('A')) + ':';
      Maske := Maske shr 1;
    end;
  end;
end;

procedure TForm1.WMDeviceChange(var Msg: TMessage);
var
  
Drive: string;
begin
  case 
Msg.wParam of
    
DBT_DeviceArrival:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DevTyp_Volume then
      begin
        
Drive := GetDrive(PDevBroadcastVolume(Msg.lParam));
        label1.Caption := 'CD inserted in Drive ' + Drive;
      end;
    DBT_DeviceRemoveComplete:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DevTyp_Volume then
      begin
        
Drive := GetDrive(PDevBroadcastVolume(Msg.lParam));
        label1.Caption := 'CD removed from Drive ' + Drive;
      end;
  end;
end;


end.

 

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