cocos2d-x 让多个小球边界碰撞

class ball :public   Sprite{//  :warning  ball后面有，public后面没有(这里千万不要看)

public:
virtual bool init();

CREATE_FUNC(ball);
virtual void update(float dt);//我们依然重写update函数达到我们自己需要的
private:
float speedX, speedY;
Size  visibleSize;//这里是速度，和可视窗口的大小
};

void ball::update(float dt){
setPosition(getPositionX()+speedX,getPositionY()+speedY);//我们先让小球运动这一次，其实我觉得应该在运动前判断是否越界的
float sw = visibleSize.width, sh = visibleSize.height, bw = getContentSize().width/2, bh= getContentSize().height/2;
float bx = getPositionX(), by = getPositionY();//我们把参数先保存起来

//判断是否越界，越界之后我们只需要把速度取负
if (bx <= bw || bx >= (sw - bw)){
speedX = -(speedX);
}
else if (by<=bh || by>=(sh-bh)){
speedY = -(speedY);
}

Sprite::initWithFile("ball.png");

visibleSize = Director::getInstance()->getVisibleSize();//获得可视窗口的大小
speedX = CCRANDOM_0_1() * 10 - 5;
speedY= CCRANDOM_0_1() * 20- 5;//随机生成小球的位置
scheduleUpdate();//更新
return true;

bool HelloWorld::init()
{
if (!LayerColor::initWithColor(Color4B(155,199,255,255)))
{
return false;
}

Size  visibleSize = Director::getInstance()->getVisibleSize();
Vec2 origin = Director::getInstance()->getVisibleOrigin();

for (int i = 0; i < 15; i++){
auto b = ball::create();
b->setPosition(CCRANDOM_0_1() * 100 + 100 + CCRANDOM_0_1() * 100, CCRANDOM_0_1() * 200 + 100);
addChild(b);
}
return true;
}