class TestLayer : public cocos2d::CCLayer

{

protected:

    cocos2d::CCSprite* cat;

    b2World* world;

public:

    TestLayer(void);

    ~TestLayer(void);

    void addNewSpriteWithCoords(cocos2d::CCPoint p);

    void update(cocos2d::ccTime dt);

    virtual void ccTouchesEnded(cocos2d::CCSet* touches, cocos2d::CCEvent* event);

};

TestLayer::TestLayer()

{

    setTouchEnabled( true );

    CCSize screenSize = CCDirector::sharedDirector()->getWinSize();

    // 定义重力向量D

    b2Vec2 gravity;

    gravity.Set(0.0f, -10.0f);

    bool doSleep = true;

    // 通过重力构建生成世界

    world = new b2World(gravity);

    world->SetAllowSleeping(doSleep);

    world->SetContinuousPhysics(true);

    // 构建地面及墙壁，因为要构建一个空心的物体，因此我们不能直接定义，而是分别定义长方体里的四个边。

    // box2d采取的现实世界的米作为计量长度的单位，所以我们要把我们的像素级的长度单位转换为米的单位就要除以PTM_RATIO（定义32像素为1米）。

    // #define PTM_RATIO 32

    b2BodyDef groundBodyDef;

    groundBodyDef.position.Set(screenSize.width//PTM_RATIO, screenSize.height//PTM_RATIO); // bottom-left corner

    //创建刚体并把刚体添加到世界上

    b2Body* groundBody = world->CreateBody(&groundBodyDef);

    // 定义刚体的形状

    b2PolygonShape groundBox;

    // bottom

    groundBox.SetAsBox(screenSize.width//PTM_RATIO, , b2Vec2(, -screenSize.height//PTM_RATIO), );

     groundBody->CreateFixture(&groundBox, );

    // top

    groundBox.SetAsBox(screenSize.width//PTM_RATIO, , b2Vec2(, screenSize.height//PTM_RATIO), );

    groundBody->CreateFixture(&groundBox, );

    // left

    groundBox.SetAsBox(, screenSize.height//PTM_RATIO, b2Vec2(-screenSize.width//PTM_RATIO, ), );

    groundBody->CreateFixture(&groundBox, );

    // right

    groundBox.SetAsBox(, screenSize.height//PTM_RATIO, b2Vec2(screenSize.width//PTM_RATIO, ), );

    groundBody->CreateFixture(&groundBox, );

    //Set up sprite

    //CCSpriteBatchNode 中的所有CCSprite只会被渲染1次，因此可以提高游戏的FPS

    CCSpriteBatchNode *mgr = CCSpriteBatchNode::create("cat.png", );

    addChild(mgr, , );

    addNewSpriteWithCoords( CCPointMake(screenSize.width/, screenSize.height/) );

    CCLabelTTF *label = CCLabelTTF::create("Tap screen", "Marker Felt", );

    addChild(label, );

    label->setColor( ccc3(,,) );

    label->setPosition( CCPointMake( screenSize.width/, screenSize.height-) );

    //定时更新，每一帧都会调用一次update函数

    scheduleUpdate();

}

TestLayer::~TestLayer()

{

    delete world;

    world = NULL;

}

//在当前的位置来产生一个精灵

void TestLayer::addNewSpriteWithCoords(CCPoint p)

{

    //创建精灵放到SpriteBatchNode里面

    CCSpriteBatchNode* batch = (CCSpriteBatchNode*)getChildByTag();

    CCSprite *sprite = CCSprite::createWithTexture(batch->getTexture());

    batch->addChild(sprite);

    //设置精灵的位置在当前的点击位置上

    sprite->setPosition( CCPointMake( p.x, p.y) );

    //定义动态刚体，然后创建到世界上去

    b2BodyDef bodyDef;

    //使刚体能够在力的作用下运行，刚体有三种：静态的、运动的、动态的

    bodyDef.type = b2_dynamicBody;

    //设置刚体的初始位置

    bodyDef.position.Set(p.x/PTM_RATIO, p.y/PTM_RATIO);

    //刚体所引用的数据就是我们所生成的精灵

    bodyDef.userData = sprite;

    b2Body *body = world->CreateBody(&bodyDef);

    //定义刚体的形状

    b2PolygonShape dynamicBox;

    dynamicBox.SetAsBox(.5f, .5f);//These are mid points for our 1m box

    //定义刚体的纹理

    b2FixtureDef fixtureDef;

    //绑定形状

    fixtureDef.shape = &dynamicBox;

    //设置密度

    fixtureDef.density = 1.0f;

    //设置摩擦

    fixtureDef.friction = 0.3f;

    body->CreateFixture(&fixtureDef);

}

void TestLayer::update(ccTime dt)

{

    int velocityIterations = ;

    int positionIterations = ;

    //Box2d是通过定期调用step来更新动画的，step的第一个参数是时间步，第二个参数是速度迭代次数，推荐8次，超过10次的基本看不出效果的提升，第三个参数是位置迭代

    world->Step(dt, velocityIterations, positionIterations);

    //遍历整个世界，找出对应精灵的刚体，进行位置更新

    for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())

    {

        if (b->GetUserData() != NULL) {

            //Synchronize the AtlasSprites position and rotation with the corresponding body

            CCSprite* myActor = (CCSprite*)b->GetUserData();

            myActor->setPosition( CCPointMake( b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO) );

            myActor->setRotation( - * CC_RADIANS_TO_DEGREES(b->GetAngle()) );

        }

    }

}

//点击屏幕事件

void TestLayer::ccTouchesEnded(CCSet* touches, CCEvent* event)

{

    //在点击的位置上创建一个新的精灵Add a new body/atlas sprite at the touched location

    CCSetIterator it;

    CCTouch* touch;

    //循环获取点击的位置

    for( it = touches->begin(); it != touches->end(); it++)

    {

        touch = (CCTouch*)(*it);

        if(!touch)

            break;

        CCPoint location = touch->getLocationInView();

        location = CCDirector::sharedDirector()->convertToGL(location);

        //在当前的位置来产生一个精灵

        addNewSpriteWithCoords( location );

    }

}