1. override
bool advanceTime(num time)

This method is called by the Juggler with the time past since the last call.

Returns true as long as this Animatable is not completed; false if it is completed.

Source 

@override
bool advanceTime(num time) {

  num newTime = _currentTime + time;

  while (newTime >= _totalTime && _repeatCount > 0) {
    _currentTime = _totalTime;
    _repeatCount--;
    _action();
    newTime -= _totalTime;
  }

  _currentTime = newTime;

  return (_repeatCount > 0);
}