本文要实现飞机射击游戏中的地图无限滚动的功能，这里分为两个层，一个层无限向下滚动，一个层无限向上滚动，这样子结合起来效果就非常有层次感，也非常逼真，这里我把地图层都写成一个类，自己把地图改下，就可以成为你自己的了！下面，我们开始吧

先来看看效果：

Cocos2d-x版本：3.4

工程环境：VS30213

一、实现思路

其实就是两张图片，然后同时一起向下（向上）滚动，当一张图片完全出视野后，就把它调到最上面。形成两个图片交替出现，不过，一般为游戏中我们都感觉像是一张图片，那是因为两张图片的头尾连接处是连起来的。原理我画了些图：

二、代码

1、无限向下滚动BackLayerDown类

头文件：

#ifndef__BackLayerDown_H__#define__BackLayerDown_H__/***功能實現無限地圖向下滾動*作者林炳文（ling20081005@126.com）*時間2015.2.27*/#include"cocos2d.h"#defineMAP_1_Tag1//宏定义两个Map的Tag#defineMAP_2_Tag2classBackLayerDown:publiccocos2d::Layer{public:virtualboolinit();CREATE_FUNC(BackLayerDown);private:voidupdate(floattime);virtualvoidonExit();};#endif//__BackLayerDown_H__

实现文件：

#include"BackLayerDown.h"USING_NS_CC;boolBackLayerDown::init(){if(!Layer::init()){returnfalse;}SizevisibleSize=Director::getInstance()->getVisibleSize();Pointorigin=Director::getInstance()->getVisibleOrigin();Sprite*map1=Sprite::create("back3_1.png");Sprite*map2=Sprite::create("back3_2.png");map1->setPosition(Vec2(visibleSize.width/2+origin.x,visibleSize.height/2+origin.y));map2->setPosition(Vec2(visibleSize.width/2+origin.x,visibleSize.height+origin.y+map2->getContentSize().height/2));this->addChild(map1,0,MAP_1_Tag);this->addChild(map2,0,MAP_2_Tag);this->scheduleUpdate();returntrue;}//移動并判斷背景voidBackLayerDown::update(floattime){SizevisibleSize=Director::getInstance()->getVisibleSize();Pointorigin=Director::getInstance()->getVisibleOrigin();Sprite*temMap1=(Sprite*)this->getChildByTag(MAP_1_Tag);Sprite*temMap2=(Sprite*)this->getChildByTag(MAP_2_Tag);temMap1->setPositionY(temMap1->getPositionY()-1);temMap2->setPositionY(temMap2->getPositionY()-1);if(temMap1->getPositionY()+temMap1->getContentSize().height/2<=origin.y){floatoffset=temMap1->getPositionY()+temMap1->getContentSize().height/2-origin.y;temMap1->setPosition(Vec2(visibleSize.width/2+origin.x,temMap1->getContentSize().height/2+origin.y+visibleSize.height+offset));}if(temMap2->getPositionY()+temMap2->getContentSize().height/2<=origin.x){floatoffset=temMap2->getPositionY()+temMap2->getContentSize().height/2-origin.y;temMap2->setPosition(Vec2(visibleSize.width/2+origin.x,temMap2->getContentSize().height/2+origin.y+visibleSize.height+offset));}}voidBackLayerDown::onExit(){this->unscheduleUpdate();Layer::onExit();}2、无限向上滚动BackLayerUp类

头文件：

#ifndef__BackLayerUp_H__#define__BackLayerUp_H__/***功能實現無限地圖向上滾動*作者林炳文（ling20081005@126.com）*時間2015.2.27*/#include"cocos2d.h"#defineMAP_1_Tag1//宏定义两个Map的Tag#defineMAP_2_Tag2classBackLayerUp:publiccocos2d::Layer{public:virtualboolinit();CREATE_FUNC(BackLayerUp);private:voidupdate(floattime);virtualvoidonExit();};#endif//__BackLayerUp_H__

实现文件：

#include"BackLayerUp.h"USING_NS_CC;boolBackLayerUp::init(){if(!Layer::init()){returnfalse;}SizevisibleSize=Director::getInstance()->getVisibleSize();Pointorigin=Director::getInstance()->getVisibleOrigin();Sprite*map1=Sprite::create("back4_2.png");Sprite*map2=Sprite::create("back4_1.png");map1->setPosition(Vec2(visibleSize.width/2+origin.x,visibleSize.height/2+origin.y));map2->setPosition(Vec2(visibleSize.width/2+origin.x,origin.y-map2->getContentSize().height/2));this->addChild(map1,0,MAP_1_Tag);this->addChild(map2,0,MAP_2_Tag);this->scheduleUpdate();returntrue;}//移動并判斷背景voidBackLayerUp::update(floattime){SizevisibleSize=Director::getInstance()->getVisibleSize();Pointorigin=Director::getInstance()->getVisibleOrigin();Sprite*temMap1=(Sprite*)this->getChildByTag(MAP_1_Tag);Sprite*temMap2=(Sprite*)this->getChildByTag(MAP_2_Tag);temMap1->setPositionY(temMap1->getPositionY()+1);temMap2->setPositionY(temMap2->getPositionY()+1);if(temMap1->getPositionY()-temMap1->getContentSize().height/2>=visibleSize.height){floatoffset=temMap1->getPositionY()-temMap1->getContentSize().height/2-visibleSize.height;temMap1->setPosition(Vec2(visibleSize.width/2+origin.x,-temMap1->getContentSize().height/2-origin.y-offset));}if(temMap2->getPositionY()-temMap2->getContentSize().height/2>=visibleSize.height){floatoffset=temMap2->getPositionY()-temMap2->getContentSize().height/2-visibleSize.height;temMap2->setPosition(Vec2(visibleSize.width/2+origin.x,-temMap2->getContentSize().height/2-origin.y-offset));}}voidBackLayerUp::onExit(){this->unscheduleUpdate();Layer::onExit();}

3、说明

其实这两个类可以写在一起的，但是这里我为了能让不同的需要分开，把它们分别写开了，要注意上面判断的方法，无限向下和无限向上判断方法是不样的，而且，这里为了防止出现黑边，要记得设置位置时要加上一定的偏移量，如上面函数中的offset,这里非常重要，如果没边上这个东东，有可能两张图片在切换时，有出现黑边。

三、使用方法

在要用到的地方，把头文件加上

#include"BackLayerDown.h"#include"BackLayerUp.h"

然后在工程的init()函数添加：

SizevisibleSize=Director::getInstance()->getVisibleSize();Pointorigin=Director::getInstance()->getVisibleOrigin();//这是地面图层this->addChild(BackLayerUp::create());//这是白云图层this->addChild(BackLayerDown::create());//加个飞机Sprite*airplane_sprite=Sprite::create("air1.png");airplane_sprite->setPosition(Vec2(visibleSize.width/2,visibleSize.height/5));this->addChild(airplane_sprite);效果：