//GameScene.h#include "cocos2d.h"USING_NS_CC;class GameScene : public cocos2d::Layer{public:    static cocos2d::Scene* createScene();        virtual bool init();        virtual bool onTouchBegan(Touch *touch, Event *unused_event);    virtual void onTouchMoved(Touch *touch, Event *unused_event);        bool isCircleCollision(Point pos1, float radius1, Point pos2, float radius2);        CREATE_FUNC(GameScene);    private:        //注意不能用auto关键字    Size size;    Sprite *sprite1, *sprite2;    Label *label;};

//GameScene.cpp//  Created by Jacedy on 14-8-11.#include "GameScene.h"USING_NS_CC;cocos2d::Scene* GameScene::createScene(){    auto scene = Scene::create();   //创建一个场景    auto layer = GameScene::create();   //创建一个图层    scene->addChild(layer);    return scene;}//初始化当前的图层bool GameScene::init(){    if(!Layer::init())      //初始化父类        return false;        //获取屏幕大小    size = Director::getInstance()->getVisibleSize();    //auto size = Director::getInstance()->getWinSize();    //添加一个图片精灵    sprite1 = Sprite::create("r1.png");    sprite1->setPosition(Vec2(size.width/2, size.height/2));    this->addChild(sprite1);        sprite2 = Sprite::create("r2.png");    sprite2->setPosition(Vec2(size.width*0.4, size.height/2));    this->addChild(sprite2);        label = Label::createWithSystemFont("No collision", "Marker Felt", 50);    label->setPosition(Vec2(size.width/2, size.height*0.7));    this->addChild(label);        //创建监听事件对象    auto listener = EventListenerTouchOneByOne::create();        //定义监听事件的回调函数    listener->onTouchBegan = CC_CALLBACK_2(GameScene::onTouchBegan, this);    listener->onTouchMoved = CC_CALLBACK_2(GameScene::onTouchMoved, this);        //在事件分发器中注册    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);        return true;}bool GameScene::onTouchBegan(Touch *touch, Event *unused_event){    //获取触屏位置    Point pos = touch->getLocation();    sprite2->setPosition(pos);        log("TouchBegan");        return true;}void GameScene::onTouchMoved(Touch *touch, Event *unused_event){    Point pos = touch->getLocation();    sprite2->setPosition(pos);        if (isCircleCollision(sprite1->getPosition(), sprite1->getContentSize().width/2, sprite2->getPosition(), sprite2->getContentSize().width/2))        label->setString("Collision!");    else        label->setString("No collision");        log("TouchMoved");}bool GameScene::isCircleCollision(Point pos1, float radius1, Point pos2, float radius2){    //运用勾股定理判断两圆是否相交    if (sqrt(pow(pos1.x - pos2.x, 2) + pow(pos1.y - pos2.y, 2)) > pow(radius1 + radius2, 2))    {        return false;    }    return true;}

补充：其实有专门的圆形碰撞检测函数：isbong( )，可以试一下。