制作飞镖忍者(1) Cocos2d-x 3.0alpha0(3)

10.当子弹碰到怪物时，怪物被消灭，子弹消失，即碰撞检测。需要在场景中跟踪目标和子弹，在HelloWorldScene.h声明如下：

    Array* _monsters;
    Array* _projectiles;

在构造函数和析构函数，添加如下：

HelloWorld::HelloWorld()
{
    _monsters = NULL;
    _projectiles = NULL;
}

HelloWorld::~HelloWorld()
{
    if (_monsters) {
        CC_SAFE_RELEASE_NULL(_monsters);
    }
    if (_projectiles) {
        CC_SAFE_RELEASE_NULL(_projectiles);
    }
}

然后在init函数中初始化这两个数组：

        this->_monsters = Array::create();
        this->_monsters->retain();
        
        this->_projectiles = Array::create();
        this->_projectiles->retain();

修改addMonster函数，为怪物精灵添加标签，并加入到数组，代码如下：

    _monster->setTag(1);
    _monsters->addObject(_monster);

修改onTouchesEnded函数，为子弹精灵添加标签，并加入到数组，代码如下：

    projectile->setTag(2);
    _projectiles->addObject(projectile);

然后修改spriteMoveFinished函数，增加如下代码：

    if (sprite->getTag() == 1) {
        _monsters->removeObject(sprite);
    }
    else if (sprite->getTag() == 2)
    {
        _projectiles->removeObject(sprite);
    }

添加如下方法：

void HelloWorld::update(float delta)
{
    Array* projectilesToDelete = Array::create();
    
    Object* pObject = NULL;
    Object* pObject2 = NULL;
    
    CCARRAY_FOREACH(_projectiles, pObject)
    {
        Sprite* projectile = (Sprite*)pObject;
        Array* monstersToDelete = Array::create();
        
        CCARRAY_FOREACH(_monsters, pObject2)
        {
            Sprite* monster = (Sprite*)pObject2;
            if (projectile->getBoundingBox().intersectsRect(monster->getBoundingBox())) {
                monstersToDelete->addObject(monster);
            }
        }
        
        CCARRAY_FOREACH(monstersToDelete, pObject2)
        {
            Sprite* monster = (Sprite*)pObject2;
            _monsters->removeObject(monster);
            this->removeChild(monster);
        }
        
        if (monstersToDelete->count() > 0) {
            projectilesToDelete->addObject(projectile);
        }
        monstersToDelete->release();
    }
    
    CCARRAY_FOREACH(projectilesToDelete, pObject)
    {
        Sprite* projectile = (Sprite*)pObject;
        _projectiles->removeObject(projectile);
        this->removeChild(projectile);
    }
    
    projectilesToDelete->release();
}

遍历子弹数组，计算每一个子弹所可能遇到的怪物，用它们各自的边界框进行交叉检测，检测到交叉，则将怪物对象放入ToDelete（待删除）数组，不能在遍历的时候删除一个对象。若是子弹遇到了怪物，也需要放入ToDelete（待删除）数组。然后从场景和数组中移动掉。同样，也在init函数，安装定时器，代码如下：