cocos2dx学习笔记：cocos2dx3.x版本程序初始化流程

cocos2dx3.x版本的程序的初始化和运行流程和2.x版本类似。之前有过笔记，不过这里还是简单的笔记下：

首先是main.cpp：

int APIENTRY _tWinMain(HINSTANCE hInstance,
                       HINSTANCE hPrevInstance,
                       LPTSTR    lpCmdLine,
                       int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // create the application instance
    AppDelegate app;
    return Application::getInstance()->run();
}

这里申请了一个变量app，然后调用了run方法。

我们先看下AppDelegate的实现代码：

class  AppDelegate : private cocos2d::Application
{
//AppDelegate 继承自Application
}
=======
AppDelegate::AppDelegate() 
{
//空的构造函数
}
bool AppDelegate::applicationDidFinishLaunching() {
    // initialize director
    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();
    if(!glview) {
        glview = GLView::create("TheWeaponRentalShop");
        director->setOpenGLView(glview);
    }

    // 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 = HelloWorld::createScene();
    // run
    director->runWithScene(scene);

    return true;
}

继续看下Application的实现：

class CC_DLL Application : public ApplicationProtocol
{
public:
    Application();
    virtual ~Application();
    int run();
    static Application* getInstance();
。。。。。    
protected:
。。。。。
    static Application * sm_pSharedApplication;
};
=====
// sharedApplication pointer
//静态成员变量初始化
Application * Application::sm_pSharedApplication = 0;

Application::Application()
: _instance(nullptr)
, _accelTable(nullptr)
{
    _instance    = GetModuleHandle(nullptr);
    _animationInterval.QuadPart = 0;
    CC_ASSERT(! sm_pSharedApplication);
    sm_pSharedApplication = this;	//调用构造函数时，会将this指针传递给sm_pSharedApplication。非常重要！！
}

Application::~Application()
{
    CC_ASSERT(this == sm_pSharedApplication);
    sm_pSharedApplication = NULL;
}

int Application::run()
{
。。。。。
    // Initialize instance and cocos2d.
    //先初始化程序运行逻辑
    if (!applicationDidFinishLaunching())
    {
        return 0;
    }

    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();

    // Retain glview to avoid glview being released in the while loop
    glview->retain();
		//程序主循环
    while(!glview->windowShouldClose())
    {
        QueryPerformanceCounter(&nNow);
        if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)//帧数控制
        {
            nLast.QuadPart = nNow.QuadPart;
            
            director->mainLoop();//程序主循环中调用director的mainLoop方法，实现游戏业务
            glview->pollEvents();	//发送各种事件（滑动，单击等）
        }
        else
        {
            Sleep(0);
        }
    }

		//游戏结束后的清理工作
    // Director should still do a cleanup if the window was closed manually.
    if (glview->isOpenGLReady())
    {
        director->end();
        director->mainLoop();
        director = nullptr;
    }
    glview->release();
    return true;
}
Application* Application::getInstance()
{
    CC_ASSERT(sm_pSharedApplication);
    return sm_pSharedApplication;//返回静态成员变量
}

这里就很清晰了，在main函数的初始化中初始化了一个实例app，会调用到Application的构造函数中，这样Application中的sm_pSharedApplication就会被赋值为该app。之后调用run方法，就会县调用到Appdelegate::applicationDidFinishLaunching,然后进入游戏主循环。