Cocos2d x 如何在层中访问物理世界

我需要在层中的两个实体之间创建关节。将在物理世界中添加接头。如何访问层中的物理世界？

我的JavaScript实现。希望这会有帮助

var space;

function initPhysics() {
    space = new cp.Space();
    space.gravity = cp.v(0, -800);
    space.iterations = 30;
    space.sleepTimeThreshold = Infinity;
    space.collisionSlop = Infinity;
}

function addJoints() {
    chainTableJoint1 = new cp.PivotJoint(chainEnd1, tableBackBody, cp.v.add(cp.v(chainEnd1.getPos().x, tableBackNode.getPosition().y + (tableBackNode.getContentSize().height * 0.5)), boxOffset));
    chainTableJoint2 = new cp.PivotJoint(chainEnd2, tableBackBody, cp.v.add(cp.v(chainEnd2.getPos().x, tableBackNode.getPosition().y + (tableBackNode.getContentSize().height * 0.5)), boxOffset));

    space.addConstraint(chainTableJoint1);
    space.addConstraint(chainTableJoint2);
}

您有四种选择：

1）覆盖层：：oneter（）或onentertTransitiondFinish（） 方法然后从主题访问，如下所示：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

2）创建一个自定义的Layer:：createScene（）方法，然后像这样从Layer:：init（）访问：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

3）向控制器添加PhysicsWorld getter方法（包括一些库代码自定义）：

首先转到CCDirector.h，然后在NS_CC_BEGIN下添加场景类的前向声明，如下所示：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

然后转到Director类的private部分，添加以下两行：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

然后转到Director类的public部分，添加如下getter方法：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

这是对CCDirector.h文件中所做更改的概述：

// CCDirector.h
NS_CC_BEGIN

// 1
class cocos2d::Scene;

class Director : public Ref{

public:
    //2
    cocos2d::PhysicsWorld* getWorld() const{
        return _myPhysicsWorld;
    };
private:
    // 3
    cocos2d::PhysicsWorld* _myPhysicsWorld;
    friend class cocos2d::Scene;
};

NS_CC_END

因此，在这之后，我们转到CCScene.cpp，进入一个具有此签名（bool Scene:：initWithPhysics（））的方法，您将发现一个对PhysicsWorld:：construct（this）的调用，该添加正好在该方法之后，调用此行：

_director->_myPhysicsWorld = _physicsWorld;

这应该是我们在CCScene.cpp中所做工作的概述：

// CCScene.cpp
class Scene : public Node{

    bool Scene::initWithPhysics(){

         _physicsWorld = PhysicsWorld::construct(this);
         // 4 since Director is a singleton class, we can access its instance from anywhere
        _director->_myPhysicsWorld = _physicsWorld;

    }
};  

现在，只要在任何地方调用Scene:：createWithPhysics（），控制器就会获得PhysicsWorld指针的副本，可以使用我们的控制器getWorld（）方法随时随地访问该指针！！（因为导演是一个单身汉，你知道）这一切都不会让用户看到“我的物理世界”，这意味着他只能从外部阅读“我的物理世界”

4）创建自己的自定义PhysicsWorld类，因为PhysicsWorld:：construct（）受到保护，这意味着它可以很容易地继承

// PhysicsManager.h

class PhysicsManager : public cocos2d::PhysicsWorld
{
public:

    static PhysicsManager* createWorld(cocos2d::Scene* scene) {
        _myPhysicsWorld = PhysicsWorld::construct(scene);
    }

    PhysicsWorld* getWorld() const { return _myPhysicsWorld; }

private:
    static cocos2d::PhysicsWorld* _myPhysicsWorld;
};

//PhysicsManager.cpp

PhysicsManager::PhysicsWorld* _myPhysicsWorld;

现在您可以这样使用它：

    Layer::onEnter(){
        Layer::onEnter();
        auto world = _director->getRunningScene()->getPhysicsWorld();
    }

Scene* GameScene::createScene()
{
    auto layer = new (std::nothrow) GameScene;
    if (layer)
    {
        auto scene = Scene::createWithPhysics();
        layer->autorelease();
        scene->addChild(layer);
        if (layer->init()) return scene;
    }
    CC_SAFE_DELETE(layer);
    return nullptr;
}

// then in Layer::init() you do this:

Layer::init(){
    auto world = _director->getRunningScene()->getPhysicsWorld();
}

NS_CC_BEGIN
class cocos2d::Scene;

private:
cocos2d::PhysicsWorld* _myPhysicsWorld;
friend class Scene;

public:
cocos2d::PhysicsWorld* getWorld() const{
    return _myPhysicsWorld;
};

Layer::init(){

    auto physicsManager = PhysicsManager::createWorld(this->getScene());

    auto world = physicsManager->getWorld();

}

记住，如果你想的话，你甚至可以把它变成一个单例类

编辑：

我忘了提到这里还有一个很好的解决方案：