Question

I am trying to handle some events when my application is idle so i created this code

procedure TForm1.ApplicationEventIdle(Sender: TObject; var Done: Boolean);
begin
      Done := false;
      ShowMessage('Hello');
      Done := true;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Application.OnIdle := ApplicationEventIdle;
end;

The problem is the message box appears infinite times how can i display it only once ?

Answer 1

This behaviour happens precisely because you show the dialog. In order to close the dialog you have to click the OK button. This places an input message on the queue. After that has been processed the OnIdle event fires. And you show the message box again. And so on and so on.

You need to make sure that you don’t do anything that requires user input in your OnIdle handler. In your case try outputting to a log rather than showing a dialog, e.g. OutputDebugString.