Question

I am not sure when Delphi creates the main form’s child components.

In my TMainForm.FormCreate() I am invoking TIdTCPClient.Connect() and TIdTCPClient.SendCmd(). My program shows up in the Windows TAsk manager, but I don’t see the GUI. However, if I disconnect the Ethernet cable & start the program, the GUI appears.

I am guessing this is because I am trying to invoke methods of a child componenet of the main form in the main form’s FormCraete() method.

Oops, I forgot to say – the TIdTCPClient is placed on the form at design time, it is not created dynamically at runtime.

Any comment? Thanks in advance

Answer 1

The problem is that Indy is blocking, and therefore stops the Create from continuing until the connection is made or times out.

You can fix this by using a custom message that you post to your form in the OnCreate event, that will delay it until the form has been displayed:

const
  UM_DOCONNECTION = WM_USER + 1;

type
  TForm1=class(TForm)
     ...
  private
    procedure UmDoConnection(var Msg: TMessage); message UM_DOCONNECTION;
    ...
  end;

  implementation

  procedure TForm1.FormCreate(Sender: TObject);
  begin
    PostMessage(Handle, UM_DOCONNECTION, 0, 0);
    // Other stuff
  end;

  procedure TForm1.UmDoConnection(var Msg: TMessage);
  begin
    IdTCPClient.Connect;
    IdTCPClient.SendCmd(...);
  end;

The best way, of course, would be to move your Indy stuff into it’s own thread so it has no connection to the main thread.