cocos2d-x C++ 原始工程引擎运行机制解析

新建一个工程，相信感兴趣的同学都想知道cocos引擎都是如何运行的

想知道是如何运行的，看懂四个文件即可

话不多说，上代码：

1、首先解释 AppDelegate.h

#ifndef  _APP_DELEGATE_H_
#define  _APP_DELEGATE_H_

#include "cocos2d.h"

/**
@brief    The cocos2d Application.

Private inheritance here hides part of interface from Director.
*/  //从这里可以看到AppDelegate继承了cocos2d::Application ，而cocos2d::Application是cocos2d-x引擎提供的基类
class  AppDelegate : private cocos2d::Application
{
public:
    AppDelegate();
    virtual ~AppDelegate();
    /*
     
     */
    virtual void initGLContextAttrs();

    /**
    @brief    Implement Director and Scene init code here.
    @return true    Initialize success, app continue.
    @return false   Initialize failed, app terminate.
        *游戏启动时调用的函数，在这里可以初始化导演对象和场景对象
    */
    virtual bool applicationDidFinishLaunching();

    /**
    @brief  Called when the application moves to the background
    @param  the pointer of the application
        *游戏进入后台时调用的函数
    */
    virtual void applicationDidEnterBackground();

    /**
    @brief  Called when the application reenters the foreground
    @param  the pointer of the application
        *游戏进入前台时调用的函数
    */
    virtual void applicationWillEnterForeground();
};

#endif // _APP_DELEGATE_H_

2、AppDelegate.cpp

#include "AppDelegate.h"
#include "HelloWorldScene.h"

USING_NS_CC;//这个是cocos2d－x提供的一个宏，它是用来替换 using namespace cocos2d语句的。

static cocos2d::Size designResolutionSize = cocos2d::Size(480, 320);
static cocos2d::Size smallResolutionSize = cocos2d::Size(480, 320);
static cocos2d::Size mediumResolutionSize = cocos2d::Size(1024, 768);
static cocos2d::Size largeResolutionSize = cocos2d::Size(2048, 1536);

AppDelegate::AppDelegate()
{
}

AppDelegate::~AppDelegate() 
{
}

// if you want a different context, modify the value of glContextAttrs
// it will affect all platforms
void AppDelegate::initGLContextAttrs()
{
    // set OpenGL context attributes: red,green,blue,alpha,depth,stencil
    GLContextAttrs glContextAttrs = {8, 8, 8, 8, 24, 8};

    GLView::setGLContextAttrs(glContextAttrs);
}

// if you want to use the package manager to install more packages,  
// don't modify or remove this function
static int register_all_packages()
{
    return 0; //flag for packages manager
}

// 游戏启动时调用的函数
bool AppDelegate::applicationDidFinishLaunching() {
    // initialize director
    auto director = Director::getInstance();//初始化导演类
    auto glview = director->getOpenGLView();
    if(!glview) {
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32) || (CC_TARGET_PLATFORM == CC_PLATFORM_MAC) || (CC_TARGET_PLATFORM == CC_PLATFORM_LINUX)
        glview = GLViewImpl::createWithRect("NotesDamo", cocos2d::Rect(0, 0, designResolutionSize.width, designResolutionSize.height));
#else
        glview = GLViewImpl::create("NotesDamo");
#endif
        director->setOpenGLView(glview);//设置导演类的OpenGL视图
    }

    // turn on display FPS
    director->setDisplayStats(true);//设置是否在屏幕上显示帧率信息(一般都是为了测试，实际发布时是不会显示的)

    // set FPS. the default value is 1.0/60 if you don't call this
    director->setAnimationInterval(1.0f / 60);//一秒执行60帧

    // Set the design resolution
    glview->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, ResolutionPolicy::NO_BORDER);
    auto frameSize = glview->getFrameSize();
    // if the frame's height is larger than the height of medium size.
    if (frameSize.height > mediumResolutionSize.height)
    {        
        director->setContentScaleFactor(MIN(largeResolutionSize.height/designResolutionSize.height, largeResolutionSize.width/designResolutionSize.width));
    }
    // if the frame's height is larger than the height of small size.
    else if (frameSize.height > smallResolutionSize.height)
    {        
        director->setContentScaleFactor(MIN(mediumResolutionSize.height/designResolutionSize.height, mediumResolutionSize.width/designResolutionSize.width));
    }
    // if the frame's height is smaller than the height of medium size.
    else
    {        
        director->setContentScaleFactor(MIN(smallResolutionSize.height/designResolutionSize.height, smallResolutionSize.width/designResolutionSize.width));
    }

    register_all_packages();

    // create a scene. it's an autorelease object
    auto scene = HelloWorld::createScene();//创建导演类对象scene

    // run
    director->runWithScene(scene);//运行该场景(会使游戏进入该场景)

    return true;
}

// This function will be called when the app is inactive. Note, when receiving a phone call it is invoked.

//游戏进入后台时调用的函数
void AppDelegate::applicationDidEnterBackground() {
    Director::getInstance()->stopAnimation();//停止场景中的动画

    // if you use SimpleAudioEngine, it must be paused
    // 停止背景音乐，默认时注释掉的
    // SimpleAudioEngine::getInstance()->pauseBackgroundMusic();
}

// this function will be called when the app is active again
// 游戏进入前台时调用的函数
void AppDelegate::applicationWillEnterForeground() {
    Director::getInstance()->startAnimation();//开始场景中的动画

    // if you use SimpleAudioEngine, it must resume here
    // 继续背景音乐的，默认是注释掉的
    // SimpleAudioEngine::getInstance()->resumeBackgroundMusic();
}

3、HelloWorldScene.h

#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__

#include "cocos2d.h"


/*
 *在这里我们可以看出，HelloWorld类继承了cocos2d::Layer类；它被称为层(layer)，这些层被放到了场景(scene)中，场景类是：cocos2d::Scene；
    注意：HelloWorld.h虽然命名为场景，但是它内部定义的HelloWorld类是一个层
 */
//HelloWorld继承了cocos2d::Layer，HelloWorld是一个层，而不是场景。
class HelloWorld : public cocos2d::Layer
{
    
public:
    
    static cocos2d::Menu* m_pSelectedItem();
    
    virtual ~HelloWorld(){}
    
    static cocos2d::Scene* createScene();//声明创建当前的层HelloWorld所在场景的静态函数createScene()；
    
    virtual bool init();//声明初始化层HelloWorld实例函数。
    
    // a selector callback
    void menuCloseCallback(cocos2d::Ref* pSender);//声明菜单回调函数menuCloseCallback，用于触摸菜单事件的回调。
    
    CREATE_FUNC(HelloWorld);//CREATE_FUNC是cocos2d-x中定义的一个宏(作用是：创建一个静态函数"static create()"，该函数可以用来创建层)；
    
    
    
    // implement the "static create()" method manually
    
};

#endif // __HELLOWORLD_SCENE_H__

4、HelloWorldScene.cpp

#include "HelloWorldScene.h"
#include "SimpleAudioEngine.h"

USING_NS_CC;
/*
 说明：createScene()函数式是在游戏应用启动的时候，在AppDelegate中的bool AppDelegate::applicationDidFinishLaunching()函数中通过 auto scene = HelloWorld::createScene()语句调用的。
    createScene()中做了三件事情，首先创建了HelloWorld层所在的场景对象，其次创建了HelloWorld层，最后将HelloWorld层添加到场景scene中；
 */
Scene* HelloWorld::createScene()
{
    // 'scene' is an autorelease object
    auto scene = Scene::create();
    
    // 'layer' is an autorelease object
    // 当调用到这句创建层的时候，会调用HelloWorld的实例函数init()，达到初始化HelloWorld层的目的。
    auto layer = HelloWorld::create();

    // add layer as a child to scene
    scene->addChild(layer);

    // return the scene
    return scene;
}

// on "init" you need to initialize your instance
bool HelloWorld::init()
{
    //////////////////////////////
    // 1. super init first
    // 初始化父类
    if ( !Layer::init() )
    {
        return false;
    }
    
    auto visibleSize = Director::getInstance()->getVisibleSize();
    Vec2 origin = Director::getInstance()->getVisibleOrigin();

    /////////////////////////////
    // 2. add a menu item with "X" image, which is clicked to quit the program
    //    you may modify it.

    // add a "close" icon to exit the progress. it's an autorelease object
    // 增加一个菜单项，单机的时候退出程序
    auto closeItem = MenuItemImage::create(
                                           "CloseNormal.png",
                                           "CloseSelected.png",
                                           CC_CALLBACK_1(HelloWorld::menuCloseCallback, this));
    
    closeItem->setPosition(Vec2(origin.x + visibleSize.width - closeItem->getContentSize().width/2 ,
                                origin.y + closeItem->getContentSize().height/2));

    // create menu, it's an autorelease object
    auto menu = Menu::create(closeItem, NULL);
    menu->setPosition(Vec2::ZERO);//自定义菜单对象的位置
    this->addChild(menu, 1);//把菜单对象添加到当前HelloWorld层上

    /////////////////////////////
    // 3. add your codes below...

    // add a label shows "Hello World"
    // create and initialize a label
    
    //添加label标签标题
    auto label = Label::createWithTTF("Hello World", "fonts/Marker Felt.ttf", 24);
    
    // position the label on the center of the screen
    label->setPosition(Vec2(origin.x + visibleSize.width/2,
                            origin.y + visibleSize.height - label->getContentSize().height));

    // add the label as a child to this layer
    this->addChild(label, 1);

    // add "HelloWorld" splash screen"
    //添加精灵，也就是cocos2d-x的logo，定义到屏幕中央
    auto sprite = Sprite::create("HelloWorld.png");

    // position the sprite on the center of the screen
    sprite->setPosition(Vec2(visibleSize.width/2 + origin.x, visibleSize.height/2 + origin.y));

    // add the sprite as a child to this layer
    this->addChild(sprite, 0);
    
    
    return true;
}

// 菜单回调函数(返回主界面)
void HelloWorld::menuCloseCallback(Ref* pSender)
{
    //Close the cocos2d-x game scene and quit the application
    Director::getInstance()->end();

    #if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)//IOS表示iOS平台
    exit(0);
#endif
    
    /*To navigate back to native iOS screen(if present) without quitting the application  ,do not use Director::getInstance()->end() and exit(0) as given above,instead trigger a custom event created in RootViewController.mm as below*/
    
    //EventCustom customEndEvent("game_scene_close_event");
    //_eventDispatcher->dispatchEvent(&customEndEvent);
    
    
    
    
//    PhysicsShape物理引擎类精灵(也属于精灵)
    
    
//    节点
    //(1)创建节点
    Node * chilNode = Node::create();
    //(2)查找子节点
    Node *node = node ->getChildByTag(123);
    //(3)增加新的子节点
    node->addChild(chilNode,0,123);
    //(4)删除子节点，并停止该节点上的一切动作
    node->removeChildByTag(123,true);
    //(5)通过NOde指针删除节点
    node ->removeChild(node);
    //(6)删除所有子节点，并停止这些节点上的一切动作
    node ->removeAllChildrenWithCleanup(true);
    //(7)从父节点中删除 node 节点，并停止该节点上的一切动作。
    node->removeFromParentAndCleanup(true);
    /*Node重要属性*/
//    setPosition; 坐标
//    setAnchorPoint(Vce2(0.5,.05)); 锚点
    
    
    
    
    //坐标
//    Vec2 touchLocation = touch ->getLocationInView();
//    Vec2 touchLocation2 = Director::getInstance()->convertToGL(touchLocation);
    
    
}


/**
 cocos2d-x的事件响应机制：即菜单层最先接收到系统事件，则排在后面的是精灵层，最后是背景层，在事件的传递过程中 ，如果有一个层处理了该事件，则排在后面的层将不再接受到该事件。
 */