2.Cocos2dx 3.2中的重力系统Box2D



1
添加Box2D相关的库

步骤1：右击项目所在的解决方案à添加—>现有项目àE:\Installed\cocos2d-x-3.2\cocos2d-x-3.2\external\Box2D\proj.win32\Box2D.vcxproj

步骤2：右击项目à生成依赖项à项目依赖项à将关于libBox2D的复选框选中

步骤3：为项目添加libBox2D的库

方法：右击项目à属性à链接器à输入—>附加依赖项à编辑，添加上libBox2d.lib，à确定

案例说明：

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：