cocos2dx3.3开发FlappyBird总结十：背景层设计

#ifndef __EngryBird__BackgroundLayer__
#define __EngryBird__BackgroundLayer__

#include "cocos2d.h"

/**
 * The game background,showing the background information
 * in the game.
 */
class BackgroundLayer : public cocos2d::Layer {
public:
  /**
   * The default constructor
   */
  BackgroundLayer();

  /**
   * The default destructor
   */
  ~BackgroundLayer();

  /**
   * The init method, will init the super init method first
   *
   * @return true if succeeded, otherwise false
   */
  virtual bool init();

  CREATE_FUNC(BackgroundLayer);

  /**
   * Get the land sprite height
   *
   * @return The height of land
   */
  static float getLandHeight();
};

#endif /* defined(__EngryBird__BackgroundLayer__) */

bool BackgroundLayer::init() {
  if (!Layer::init()) {
    return false;
  }

  // Get the current time, judge whether now is day or night
  time_t t = time(NULL);
  tm *localTime = localtime(&t);
  int hour = localTime->tm_hour;

  std::string bgName;
  if (hour >= 6 && hour <= 17) {
    bgName = "bg_day";
  } else {
    bgName = "bg_night";
  }

  auto bgSprite = Sprite::createWithSpriteFrame(AtlasLoader::getInstance()->getSpriteFrame(bgName));
  // 这里设置成(0,0)，就可以从左下角开始显示至全屏
  bgSprite->setAnchorPoint(Vec2::ZERO);
  bgSprite->setPosition(Vec2::ZERO);
  this->addChild(bgSprite);

  return true;
}

// 其实就是加载地面精灵，然后获取其内容大小的高度
float BackgroundLayer::getLandHeight() {
  auto spriteFrame = AtlasLoader::getInstance()->getSpriteFrame("land");
  auto land = Sprite::createWithSpriteFrame(spriteFrame);

  return land->getContentSize().height;
}