cocos2dx解析helloworld项目源码

上一章（http://www.52php.cn/article/p-veeasfti-ho.html）中我们讲解了mac下的cocos2dx环境的搭建，并且创建了helloworld项目，这一章我们就来解读这个helloworld项目。

1.用xcode打开我们的项目，会得到如下图的目录结构：

在这里我们重点关注mac目录和classes目录，打开了一个mac项目，我们第一反应肯定是去看mac下的目录：

mac目录下有两个代码文件，我们看到main.cpp就知道，这是项目的入口处了。

2.main.cpp文件的解读：

打开main.cpp，我们可以看到main.cpp的源码如下：

/****************************************************************************
 Copyright (c) 2010 cocos2d-x.org
 
 http://www.cocos2d-x.org
 
 Permission is hereby granted,free of charge,to any person obtaining a copy
 of this software and associated documentation files (the "Software"),to deal
 in the Software without restriction,including without limitation the rights
 to use,copy,modify,merge,publish,distribute,sublicense,and/or sell
 copies of the Software,and to permit persons to whom the Software is
 furnished to do so,subject to the following conditions:
 
 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS",WITHOUT WARRANTY OF ANY KIND,EXPRESS OR
 IMPLIED,INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,DAMAGES OR OTHER
 LIABILITY,WHETHER IN AN ACTION OF CONTRACT,TORT OR OTHERWISE,ARISING FROM,OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ****************************************************************************/

#include "AppDelegate.h"
#include "cocos2d.h"

USING_NS_CC;

int main(int argc,char *argv[])
{
    AppDelegate app;
    return Application::getInstance()->run();
}

为了对代码了解，我会在代码上书写注释，这样就好了。

3.AppDelegate.cpp源码解析：

#include "AppDelegate.h" //引入头文件
#include "HelloWorldScene.h" //引入helloworldsecene的文件，该类主要是创建场景和层的将在下一步讲解该类

USING_NS_CC; //定义命名空间为cocos2d，这样引用类和方法时比较方便，其源码为：#define USING_NS_CC                     using namespace cocos2d

AppDelegate::AppDelegate() {

}

AppDelegate::~AppDelegate() 
{
}

bool AppDelegate::applicationDidFinishLaunching() {//应用开始时所做的工作
    // initialize director
    auto director = Director::getInstance(); //创建一个导演，关于导演，场景，层和精灵的关系将在文章最后讲到
    auto glview = director->getOpenGLView();//该导演打开了gl的端口
    if(!glview) {
        glview = GLView::create("My Game"); //创建为  my game
        director->setOpenGLView(glview); //将创建的设置进去
    }

    // turn on display FPS
    director->setDisplayStats(true);//true显示fps

    // set FPS. the default value is 1.0/60 if you don't call this
    director->setAnimationInterval(1.0 / 60);//每秒显示的fps数

    // create a scene. it's an autorelease object
    auto scene = HelloWorld::createScene();//得到场景，该场景是从helloworld中创建的

    // run
    director->runWithScene(scene);//运行这个场景

    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() {//应用在后台运行时所做的工作
    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() {//应用被唤醒时所做的工作
    Director::getInstance()->startAnimation();

    // if you use SimpleAudioEngine,it must resume here
    // SimpleAudioEngine::getInstance()->resumeBackgroundMusic();
}

#include "HelloWorldScene.h"

USING_NS_CC;//定义命名空间为cocos2d，这样引用类和方法时比较方便，其源码为：#define USING_NS_CC                     using namespace cocos2d

Scene* HelloWorld::createScene()//创建场景的方法
{
    // 'scene' is an autorelease object
    auto scene = Scene::create(); //创建场景

    // 'layer' is an autorelease object
    auto layer = HelloWorld::create();//创建层，由头文件：class HelloWorld : public cocos2d::Layer可以看出该类自己就是一个层

    // add layer as a child to scene
    scene->addChild(layer);//将层加入到场景中

    // return the scene
    return scene;//返回场景
}

// on "init" you need to initialize your instance
bool HelloWorld::init()//init方法系统会自动去调用
{
    //////////////////////////////
    // 1. super init first
    if ( !Layer::init() )
    {
        return false;
    }
    
    Size 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
    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);
    this->addChild(menu,1);

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

    // add a label shows "Hello World"
    // create and initialize a label
    
    auto label = LabelTTF::create("Hello World","Arial",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"
    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;
}


void HelloWorld::menuCloseCallback(Ref* pSender)
{
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WP8) || (CC_TARGET_PLATFORM == CC_PLATFORM_WINRT)
	MessageBox("You pressed the close button. Windows Store Apps do not implement a close button.","Alert");
    return;
#endif

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

#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
    exit(0);
#endif
}

5.导演，场景，层与精灵的阐述：

游戏和戏剧的区别就是游戏里你是半个编剧而戏剧里你只是一个观众，游戏你可以参与，戏剧你只能观看。何为半个编剧，即是你能够按照已经设定好的规则来指挥演员来演出。

游戏里的导演和戏剧的导演一样，就是按照剧本来指挥演员等元素来呈现一个画面，音乐等。我们以演出《雷雨》为例。

导演就是根据《雷雨》的剧本来导出所有的视觉听觉等五官效果。

场景就是《雷雨》里某一幕，拿侍萍控诉周朴园来说，这一幕就是一个场景。

层就是场景里的3维关系，在这里，天空乌云密布，天空为一层，院子里花草摇曳，院子为一层，大厅里侍萍控诉周朴园，大厅为一层，这些层组成了一幕。

精灵就是演员了，之所以称为精灵是因为这些演员不全是人。在天空这一层，乌云是精灵，他们有动作，有形态。在院子里花，草，树木都是精灵，它们也有各自的动作和形态。大厅里侍萍和周朴园也是精灵。

由此可以看出，我们写游戏的时候不妨把自己看成一个拿着半个剧本在拍戏的剧作人。下一章我们将创建自己的场景并运行它。

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!