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How do I suspend a timer ?

Posted on 1999-01-20
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Last Modified: 2010-04-06
Is there any way to temporarily suspend a timer ? I'm writing a small automatic file back-up program (hopefully to run as a Tray Icon application) and would like to suspend the timer while the user is changing their back-up options (to prevent a back up going off while the user is changing things). At first I thought to set the interval property to 0 while the user is changing their options, but if I reset interval to it's original value afterwards then the timer starts from scratch again. Is there some way round this or am I barking up the wrong tree by trying to use the timer for this ?

Thanks


Matt Freake
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Question by:paninaro
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9 Comments
 
LVL 12

Expert Comment

by:rwilson032697
Comment Utility
You could set enabled to false, then set it to true again to set it going again. Though I am not sure if this will restart the timer again from scratch. If this works dibs on the answer!

Cheers,

Raymond.
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Expert Comment

by:kretzschmar
Comment Utility
Hi paninaro,

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if YourGlobalVarInEdit then
    DoNothing
  else
    otherStuff;
end;

YourGlobalVarInEdit typ Boolean initialized False
By Begin of Usermanipulatuin set to true
on End to False

Other Solution is to disable the Timer if true
instead

donothing

Timer1.Enabled := False;

must be enabled after Usermanipiulation

meikl
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Madshi earned 200 total points
Comment Utility
Hi Matt,

I've written a little component for you...
Go to "component -> install component" and install this unit.
You can use the "Suspended" property.

unit exttimer;

interface

uses extCtrls;

type
  TExtTimer = class (TTimer)
  private
    FSuspended : boolean;
    FFireEvent : boolean;
    procedure SetSuspended (value: boolean);
  protected
    procedure Timer; override;
  published
    property Suspended : boolean read FSuspended write SetSuspended;
  end;

procedure Register;

implementation

uses classes;

procedure TExtTimer.Timer;
begin
  if FSuspended then begin
    enabled:=false;
    FFireEvent:=true;
  end else inherited;
end;

procedure TExtTimer.SetSuspended(value: boolean);
begin
  if value<>FSuspended then begin
    FSuspended:=value;
    if FFireEvent then begin
      FFireEvent:=false;
      inherited Timer;
      enabled:=true;
    end;
  end;
end;

procedure Register;
begin
  RegisterComponents('Madshi', [TExtTimer]);
end;

end.

Regards, Madshi.

P.S.: Disabling/Enabling the timer starts it from the scratch...
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Expert Comment

by:rwilson032697
Comment Utility
Madshi: Doesn't your solution effectively just toggle the enabled property?
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LVL 20

Expert Comment

by:Madshi
Comment Utility
Raymond,

nope... That would be a joke, wouldn't it???

Let's say we have a timer that fires every 10 seconds. Then you suspend the timer after the 12 second for 5 seconds, then the suspend has no effect in my timer routine. The next event fires after 10, 20, 30... seconds. If you would use the enabled property, the next event would fire after 10, 27, 37... seconds!
If the timer is suspended after the 17 second for 5 seconds, then the 20 second timer doesn't fire. But my component remembers that there's an event delay. So in the moment when you resume the timer, the event is fired at once. That means my component would fire at 10, 22, 32, 42... If you would use the enabled property, the timer would fire at 10, 32, 42...

You see the difference?

Matt,

please look at the examples I've given in this comment. Does my component react the way you want it to?
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Author Comment

by:paninaro
Comment Utility
Thanks, I've just installed the component and it works fine. I have to admit to not thinking it all through properly in the first place and following a discussion with a colleague have realised that, in an ideal world, the component would reset itself to it's old pattern once it had dealt with an abnormal event (in your last example it would fire at 10, 22, 30, 40...). Is that an easy modification to your component ?

Either way, the points are yours, let me know.

Thanks


Matt
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Expert Comment

by:Madshi
Comment Utility
Hmmm. What if you suspend the timer at 17 for 15 seconds?
Do you want to have 10,32,32,40,50,... or 10,32,40,50,... ?
The first case is not so nice. In the second case one timer event would be lost...

Regards, Madshi.
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by:Madshi
Comment Utility
Hmm. If you still want me to modify the component, you've got to let me know how exactly (see my last comment). If you're satisfied with the current solution: fine...   :-)

Regards, Madshi-
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Author Comment

by:paninaro
Comment Utility
That's OK, I've actually decided to write this particular application slightly differently. However I'm sure the timer will come in very useful with some other stuff I'm doing soon.

Many thanks

Matt
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