2.Cocos2dx 3.2中的重力系统Box2D

1.编写T32.h

#ifndef __T32_H__

#define __T32_H__

#include "cocos2d.h"

USING_NS_CC;

#define winSize Director::getInstance()->getWinSize()

#define CCLog cocos2d::log

#endif

2.编写TBack.h

#ifndef __TBack_H__

#define __TBack_H__

#include "T32.h"

class TBack : public Layer

{

public:

    CREATE_FUNC(TBack);

    bool init();

};

#endif

3编写TBack.cpp

#include "TBack.h"

bool TBack::init()

{

    Layer::init();

    setLocalZOrder(100);

    Menu* menu = Menu::create();

    MenuItemImage* item = MenuItemImage::create("CloseNormal.png", "CloseSelected.png",

        [](Ref*){

        Director::getInstance()->popScene();

    });

    menu->addChild(item);

    item->setPosition(winSize.width / 2 - item->getBoundingBox().size.width / 2,

        item->getBoundingBox().size.height / 2 - winSize.height / 2);

    addChild(menu);

    return true;

}

4.编写T06Box2D.h

#ifndef __T06Box2D_H__

#define __T06Box2D_H__

#include "T32.h"

#include "Box2D/Box2D.h"

class T06Box2D : public Layer

{

public:

    CREATE_FUNC(T06Box2D);

    bool init();

    b2World* _world;

    b2Body* _bat;

    void update(float);

};

#endif

5编写：T06Box2D.cpp

#include "T06Box2D.h"

#define PTM_RATIO 32.0f

bool T06Box2D::init()

{

    Layer::init();

    //创建世界,后面的-9.8表示向下的重力加速度为9.8

    //b2Vec2 gravity(0,-9.8f);

    //这个表示没有重力加速度

    b2Vec2 gravity(0,0.0f);

    _world = new b2World(gravity);

    {

        b2BodyDef def;

        //这里是一个动态的body，默认是静态的body

        def.type = b2_dynamicBody;

        //设置位置，要转换成重力场中的位置要除以PTM_RATIO

        def.position.Set(winSize.width / 2 / PTM_RATIO, winSize.height / 2 / PTM_RATIO);

        b2Body* body = _world->CreateBody(&def);

        //让body受力

        body->SetLinearVelocity(b2Vec2(10,20));

        //显示body的精灵

        Sprite* sprite = Sprite::create("CloseNormal.png");

        addChild(sprite);

        sprite->setPosition(body->GetPosition().x*PTM_RATIO, body->GetPosition().y*PTM_RATIO);

        //设置body的形状，让它和sprite相一致,是圆形的

        b2CircleShape shape;

        //设置半径

        shape.m_radius = sprite->getContentSize().width / 2 / PTM_RATIO;

        //后面的一个参数表示的是密度系数

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        //设置摩擦系统

        fixture->SetFriction(0.0f);

        //弹性系数

        fixture->SetRestitution(1.0f);

        //关联body和精灵

        body->SetUserData(sprite);

    }

    //加个地板

    {

        b2BodyDef def;

        // def.position.Set(0, 0);

        b2Body* body = _world->CreateBody(&def);

        //设置边界类型的形状

        b2EdgeShape shape;

        //设置地板的开始点和结束点

        shape.Set(b2Vec2(0, 0), b2Vec2(winSize.width / PTM_RATIO, 0));

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        //设置摩擦系数

        fixture->SetFriction(0.0f);

        //设置弹性系数

        fixture->SetRestitution(1.0f);

    }

    //加个天花板

    {

        b2BodyDef def;

        def.position.Set(0, winSize.height / PTM_RATIO);

        b2Body* body = _world->CreateBody(&def);

        b2EdgeShape shape;

        shape.Set(b2Vec2(0, 0), b2Vec2(winSize.width / PTM_RATIO, 0));

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        //摩擦系统

        fixture->SetFriction(0.0f);

        //弹性系数

        fixture->SetRestitution(1.0f);

    }

    //左挡板

    {

        b2BodyDef def;

        //def.position.Set(0, winSize.height / PTM_RATIO);

        b2Body* body = _world->CreateBody(&def);

        b2EdgeShape shape;

        shape.Set(b2Vec2(0, 0), b2Vec2(0, winSize.height / PTM_RATIO));

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        fixture->SetFriction(0.0f); //摩擦系统

        fixture->SetRestitution(1.0f); //弹性系数

    }

    //右挡板

    {

        b2BodyDef def;

        def.position.Set(winSize.width / PTM_RATIO, 0);

        b2Body* body = _world->CreateBody(&def);

        b2EdgeShape shape;

        shape.Set(b2Vec2(0, 0), b2Vec2(0, winSize.height / PTM_RATIO));

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        //摩擦系数

        fixture->SetFriction(0.0f);

        //弹性系数

        fixture->SetRestitution(1.0f);

    }

    //球拍

    {

        b2BodyDef def;

        def.position.Set(winSize.width / 2 / PTM_RATIO, winSize.height / 4 / PTM_RATIO);

        b2Body* body = _world->CreateBody(&def);

        _bat = body;

        Sprite* sprite = Sprite::create("bat.png");

        body->SetUserData(sprite);

        addChild(sprite);

        sprite->setPosition(body->GetPosition().x*PTM_RATIO, body->GetPosition().y*PTM_RATIO);

        Size batSize = Size(100,30);

        Size content = sprite->getContentSize();

        sprite->setScale(batSize.width / content.width, batSize.height / content.height);

        b2PolygonShape shape;

        shape.SetAsBox(batSize.width / 2 / PTM_RATIO, batSize.height / 2 / PTM_RATIO);

        b2Fixture* fixture = body->CreateFixture(&shape, 1.0f);

        //摩擦系统

        fixture->SetFriction(0.0f);

        //弹性系统

        fixture->SetRestitution(1.0f);

        //touch

        EventListenerTouchOneByOne* ev = EventListenerTouchOneByOne::create();

        ev->onTouchBegan = [](Touch*, Event*){return true; };

        ev->onTouchMoved = [&](Touch* touch, Event*){

            float dx = touch->getDelta().x / PTM_RATIO;

            b2Vec2 pos = _bat->GetPosition();

            pos.x += dx;

            //下面的函数等价于setPosition()

            _bat->SetTransform(pos, 0);

        };

        _eventDispatcher->addEventListenerWithSceneGraphPriority(ev, this);

    }

    scheduleUpdate();

    return true;

}

void T06Box2D::update(float dt)

{

      //时间在流逝

    _world->Step(dt, 8, 1);

    //遍历这个世界的body

    b2Body* body = _world->GetBodyList();

    while (body)

    {

        //设置body相关的精灵的位置

        Sprite* sprite = (Sprite*)body->GetUserData();

        if (sprite)

        {

            sprite->setPosition(body->GetPosition().x*PTM_RATIO, body->GetPosition().y*PTM_RATIO);

            sprite->setRotation(body->GetAngle()*180.0 / M_PI);

        }

        body = body->GetNext();

    }

}

6.编写TMenu.h

#ifndef __TMenu_H__

#define __TMenu_H__

#include "T32.h"

class TMenu : public Layer

{

public:

    CREATE_FUNC(TMenu);

    bool init();

    bool TouchBegan(Touch*, Event*);

};

#endif

7. 编写：TMenu.cpp

#include "TMenu.h"

#include "TBack.h"

#include "T01CPP11.h"

#include "T02Vector.h"

#include "T03Map.h"

#include "T04Label.h"

#include "T06Box2D.h"

static const char* title[] = {

    "T01CPP11",

    "T02Vector",

    "T03Map",

    "T04Label",

    "T06Box2D"

};

bool TMenu::init()

{

    Layer::init();

    Menu* menu = Menu::create();

    addChild(menu);

    for (int i = 0; i < sizeof(title) / sizeof(*title); ++i)

    {

        MenuItemFont* item = MenuItemFont::create(title[i], [](Ref* sender){

            MenuItem* item = (MenuItem*)sender;

            int i = item->getTag()-1000;

            Layer* l = NULL;

            if (title[i] == "T01CPP11")  l = T01CPP11::create();

            if (title[i] == "T02Vector") l = T02Vector::create();

            if (title[i] == "T03Map") l = T03Map::create();

            if (title[i] == "T04Label") l = T04Label::create();

            if (title[i] == "T06Box2D") l = T06Box2D::create();

            if (l)

            {

                TBack* b = TBack::create();

                Scene* s = Scene::create();

                s->addChild(b);

                s->addChild(l);

                Director::getInstance()->pushScene(s);

            }

        });

        menu->addChild(item);

        item->setTag(1000 + i);

    }

    menu->alignItemsVertically();

    // 触摸

    auto ev = EventListenerTouchOneByOne::create();

#if 0

    ev->onTouchBegan = [](Touch*, Event*){

        return true;

    };

#endif

    //ev->onTouchBegan = std::bind(&TMenu::TouchBegan, this, std::placeholders::_1, std::placeholders::_2);

    ev->onTouchBegan = CC_CALLBACK_2(TMenu::TouchBegan, this);

    ev->onTouchMoved = [&](Touch* touch, Event*){

        setPositionY(getPositionY() + touch->getDelta().y);

    };

    _eventDispatcher->addEventListenerWithSceneGraphPriority(ev, this);

    return true;

}

bool TMenu::TouchBegan(/*TMEnu* this, */Touch*, Event*)

{

    return true;

}

8.编写AppDelegate.cpp

#include "AppDelegate.h"

#include "TMenu.h"

#include "TBack.h"

USING_NS_CC;

AppDelegate::AppDelegate() {

}

AppDelegate::~AppDelegate()

{

}

bool AppDelegate::applicationDidFinishLaunching() {

    // initialize director

    auto director = Director::getInstance();

    auto glview = director->getOpenGLView();

    if(!glview) {

        glview = GLView::create("My Game");

        glview->setFrameSize(480, 320);

        director->setOpenGLView(glview);

    }

    glview->setDesignResolutionSize(480, 320, ResolutionPolicy::EXACT_FIT);

    // turn on display FPS

    director->setDisplayStats(true);

    // set FPS. the default value is 1.0/60 if you don't call this

    director->setAnimationInterval(1.0 / 60);

    // create a scene. it's an autorelease object

    auto scene = Scene::create();

    scene->addChild(TMenu::create());

    scene->addChild(TBack::create());

    // run

    director->runWithScene(scene);

    return true;

}

// This function will be called when the app is inactive. When comes a phone call,it's be invoked too

void AppDelegate::applicationDidEnterBackground() {

    Director::getInstance()->stopAnimation();

    // if you use SimpleAudioEngine, it must be pause

    // SimpleAudioEngine::getInstance()->pauseBackgroundMusic();

}

// this function will be called when the app is active again

void AppDelegate::applicationWillEnterForeground() {

    Director::getInstance()->startAnimation();

    // if you use SimpleAudioEngine, it must resume here

    // SimpleAudioEngine::getInstance()->resumeBackgroundMusic();

}

运行效果：