需要引入的头文件

#include "cocos2d.h"
#include "Box2D\Box2D.h"
#include <string>

创建物理世界

world = new b2World(b2Vec2(0,-10));

创建会自由掉落的 精灵

bird = Sprite::create("bird0_0.png");
    bird->setName("bird");
    Size size = bird->getContentSize();
    b2BodyDef def;
    def.type = b2_dynamicBody;
    def.position = b2Vec2(screenSize.width / 4 / RATIO, screenSize.height / 2 / RATIO + 1);//鸟的位置
    b2PolygonShape shape;
    shape.SetAsBox(size.width/2/RATIO,size.height/2/RATIO); //碰撞体积？
    b2FixtureDef fixtureDef;
    fixtureDef.density = 1;
    fixtureDef.friction = 0.3;
    fixtureDef.shape = &shape;
    b2Body *body = world->CreateBody(&def);
    body->CreateFixture(&fixtureDef);
    addChild(bird);
    bird->setPosition(Point(def.position.x*RATIO, def.position.y*RATIO));//物理物体会自动往下掉 因此绑定物理物体的位置到sprite上 就形成了物理
    body->SetUserData(bird);//与sprite绑定
    this->body = body;

必须将精灵与物理盒子绑定才能实现物理效果   此方法必须每秒执行，不停的将精灵与物理盒子位置绑定

void HelloWorld::bingSprite(){ //让物理盒子和精灵实时绑定来达到物理效果 物理盒子本身是看不到的
    Sprite *s;
    for (b2Body *b = world->GetBodyList(); b; b = b->GetNext()){
        s = (Sprite*)b->GetUserData();
        if (b->GetUserData() && b->GetType() == b2_dynamicBody||b->GetType()==b2_kinematicBody){
            if (s != NULL){
                s->setPosition(b->GetPosition().x*RATIO, b->GetPosition().y*RATIO);//每次渲染都让sprite与box body保持位置绑定
            }
            
        }
    }
}

)

添加道路物体  精灵下落时会落在上面

Sprite *ground = Sprite::create("land.png");
    Size size = ground->getContentSize();
    ground->setScaleX(2);
    ground->setScaleY(2);
    b2BodyDef bDef;
    bDef.type = b2_staticBody;
    bDef.position = b2Vec2(size.width/2/RATIO,size.height/2/RATIO);//设置碰撞物体的位置
    b2PolygonShape groundShape;
    groundShape.SetAsBox(size.width/2/RATIO,size.height/2/RATIO-0.3);//position 和SetAsBox 都可以改变碰撞物体的位置 不知为何
    b2Body *groundBody = world->CreateBody(&bDef);
    b2FixtureDef fix;
    fix.shape = &groundShape;
    groundBody->CreateFixture(&fix);
    groundBody->SetUserData(ground);
    addChild(ground);

linearVelocity  是设置盒子执行的动作 如 往各个方向移动

物理盒子有 三种类型 漂浮物体  静态物体 和动态物体 

漂浮物体不受重力音响 可自由移动，静态物体位置是固定的不会掉落， 动态物体会自由掉落

笔记至此结束