{  this.activityScheduler.setActivityState(new ActivityPresentationState( this.activityScheduler, this.activity));  }
{  this.activityScheduler.setActivityState(new ActivityPresentationState( this.activityScheduler, this.activity, true));  }
    public void previous()    {        // on renvoie a la presentation d'activite        this.activityScheduler.setActivityState(new ActivityPresentationState(                this.activityScheduler, this.activity));    }