Question

Dear Delphi programmers,

I’m looking for help how to write a one-shot timer (No GUI, so VCL Timers out of question)…

Let me explain a little bit more.

In my code (explaining with VCL timer but in this particular project I have no forms):

1. Call a procedure which send a char over serial port
2. Enable a timer with a X amount of Interval

In the OnTimer event:

I have a code which send a char then disable the timer itself to never be executed again.

The problem is that I need to make the creation of these timers dynamic.
I thought of the function SetTimer() then KillTimer() in the “OnTimer event” to disable it (free it).

Is it a good (safe) way?

Thank you!

Answer 1

Is it safe to kill timer from inside of a timer event ?

Yes, that’s perfectly safe.

How to implement simplest one shot timer ?

The easiest implementation of a 1 second one shot timer is this, but note, that if you start more of them, you won’t be able to distinguish which one of them elapsed its interval:

procedure TimerProc(hwnd: HWND; uMsg: UINT; idEvent: UINT_PTR;
  dwTime: DWORD); stdcall;
begin
  KillTimer(0, idEvent);
  ShowMessage('I''m done!');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  SetTimer(0, 0, 1000, @TimerProc);
end;