|Opening and Closing a CD Tray|
How can I open and close the tray on a CD-ROM drive?
Most of you are probably familiar with the TMediaPlayer component. It's a nice multi-purpose component for multimedia. But it has one failing and that is its inability to close a CD-ROM drive tray if it's open. And unfortunately for us, there's no way to manipulate methods or properties of TMediaPlayer to enable this functionality. So what we have to do is use the Windows API; in particular, we'll be using the MMSystem.pas file.
One thing to note: We can use Windows API function calls solely, but TMediaPlayer does some internal handling that we don't need to worry about if we employ the component. So this example makes use of the TMediaPlayer.
Just follow these steps:
procedure TForm1.Button2Click(Sender: TObject); begin with MediaPlayer1 do if (MediaPlayer1.Mode = mpOpen) then mciSendCommand(MediaPlayer1.DeviceID, MCI_SET, MCI_SET_DOOR_CLOSED, 0) else mciSendCommand(MediaPlayer1.DeviceID, MCI_SET, MCI_SET_DOOR_OPEN, 0); end;
Notice we use the function mciSendCommand. This is the "Swiss Army Knife" of the MMSystem unit. In Windows, everything's controlled by messages. With respect to device control, mciSendCommand is very similar to a window's WndProc in that it acts as a message dipatcher. Just supply the device, the message type, message flags, and message parameters, and you're on your way. For more detailed information, I suggest you look in the help file.
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