reset method

void reset()

当雪花移出屏幕时，需要重置参数

Implementation

void reset() {
  double ratio = 1.0;

  if (weatherType == WeatherType.lightRainy) {
    ratio = 0.5;
  } else if (weatherType == WeatherType.middleRainy) {
    ratio = 0.75;
  } else if (weatherType == WeatherType.heavyRainy ||
      weatherType == WeatherType.thunder) {
    ratio = 1;
  } else if (weatherType == WeatherType.lightSnow) {
    ratio = 0.5;
  } else if (weatherType == WeatherType.middleSnow) {
    ratio = 0.75;
  } else if (weatherType == WeatherType.heavySnow) {
    ratio = 1;
  }
  if (WeatherUtil.isRainy(weatherType)) {
    double random = 0.4 + 0.12 * Random().nextDouble() * 5;
    this.scale = random * 1.2;
    this.speed = 30 * random * ratio * heightRatio;
    this.alpha = random * 0.6;
    x = Random().nextInt(width * 1.2 ~/ scale).toDouble() -
        width * 0.1 ~/ scale;
  } else {
    double random = 0.4 + 0.12 * Random().nextDouble() * 5;
    this.scale = random * 0.8 * heightRatio;
    this.speed = 8 * random * ratio * heightRatio;
    this.alpha = random;
    x = Random().nextInt(width * 1.2 ~/ scale).toDouble() -
        width * 0.1 ~/ scale;
  }
}