code: public void setWarning (float warnPercent, ResultListener<TimerView> warner)
      {
          // This warning hasn't triggered yet
          _warned = false;
  
          // Here are the details
          _warnPercent = warnPercent;
          _warner = warner;
      }
docs: Setup a warning to trigger after the timer is "warnPercent"
  or more completed.  If "warner" is non-null, it will be
  called at that time.