Cocos2d-x学习笔记（二） 永远的HelloWorld

 1 int APIENTRY _tWinMain(HINSTANCE hInstance,
 2                        HINSTANCE hPrevInstance,
 3                        LPTSTR    lpCmdLine,
 4                        int       nCmdShow)
 5 {
 6     UNREFERENCED_PARAMETER(hPrevInstance);
 7     UNREFERENCED_PARAMETER(lpCmdLine);
 8 
 9     // create the application instance
10     AppDelegate app;
11     CCEGLView* eglView = CCEGLView::sharedOpenGLView();
12     eglView->setFrameSize(960, 640 );
13     return CCApplication::sharedApplication()->run();
14 }

1 #define APIENTRY    WINAPI

1 #define WINAPI      __stdcall

1 #ifdef _UNICODE
2 
3     #define _tWinMain wWinMain
4 
5 #else
6 
7     #define _tWinMain WinMain
8 
9 #endif

1.3  UNREFERENCED_PARAMETER

1 UNREFERENCED_PARAMETER(hPrevInstance);
2 UNREFERENCED_PARAMETER(lpCmdLine);

1 #define UNREFERENCED_PARAMETER(P)          (P)

 1 class CC_DLL CCApplicationProtocol
 2 {
 3 public:
 4 
 5     virtual ~CCApplicationProtocol() {}
 6 
 7     /**
 8     @brief    Implement CCDirector and CCScene init code here.
 9     @return true    Initialize success, app continue.
10     @return false   Initialize failed, app terminate.
11     */
12     virtual bool applicationDidFinishLaunching() = 0;
13 
14     /**
15     @brief  The function be called when the application enter background
16     @param  the pointer of the application
17     */
18     virtual void applicationDidEnterBackground() = 0;
19 
20     /**
21     @brief  The function be called when the application enter foreground
22     @param  the pointer of the application
23     */
24     virtual void applicationWillEnterForeground() = 0;
25 
26     /**
27     @brief    Callback by CCDirector for limit FPS.
28     @interval       The time, expressed in seconds, between current frame and next. 
29     */
30     virtual void setAnimationInterval(double interval) = 0;
31 
32     /**
33     @brief Get current language config
34     @return Current language config
35     */
36     virtual ccLanguageType getCurrentLanguage() = 0;
37     
38     /**
39      @brief Get target platform
40      */
41     virtual TargetPlatform getTargetPlatform() = 0;
42 };

1 #if defined(_USRDLL)
2     #define CC_DLL     __declspec(dllexport)
3 #else         /* use a DLL library */
4     #define CC_DLL     __declspec(dllimport)
5 #endif

 1 class CC_DLL CCApplication : public CCApplicationProtocol
 2 {
 3 public:
 4     CCApplication();
 5     virtual ~CCApplication();
 6 
 7     /**
 8     @brief    Run the message loop.
 9     */
10     int run();
11 
12     /**
13     @brief    Get current applicaiton instance.
14     @return Current application instance pointer.
15     */
16     static CCApplication* sharedApplication();
17 
18     /* override functions */
19     virtual void setAnimationInterval(double interval);
20     virtual ccLanguageType getCurrentLanguage();
21     
22     /**
23      @brief Get target platform
24      */
25     virtual TargetPlatform getTargetPlatform();
26 
27     /* set the Resource root path */
28     void setResourceRootPath(const std::string& rootResDir);
29 
30     /* get the Resource root path */
31     const std::string& getResourceRootPath(void)
32     {
33         return m_resourceRootPath;
34     }
35 
36     void setStartupScriptFilename(const std::string& startupScriptFile);
37 
38     const std::string& getStartupScriptFilename(void)
39     {
40         return m_startupScriptFilename;
41     }
42 
43 protected:
44     HINSTANCE           m_hInstance;
45     HACCEL              m_hAccelTable;
46     LARGE_INTEGER       m_nAnimationInterval;
47     std::string         m_resourceRootPath;
48     std::string         m_startupScriptFilename;
49 
50     static CCApplication * sm_pSharedApplication;
51 };

1 CCApplication::CCApplication()
2     : m_hInstance(NULL)
3     , m_hAccelTable(NULL)
4 {
5     m_hInstance    = GetModuleHandle(NULL);
6     m_nAnimationInterval.QuadPart = 0;
7     CC_ASSERT(! sm_pSharedApplication);
8     sm_pSharedApplication = this;
9 }

int APIENTRY _tWinMain(HINSTANCE hInstance,
                       HINSTANCE hPrevInstance,
                       LPTSTR    lpCmdLine,
                       int       nCmdShow)
{
     // create the application instance
    AppDelegate app;
    CCEGLView* eglView = CCEGLView::sharedOpenGLView();
    eglView->setFrameSize(960, 640 );
    return CCApplication::sharedApplication()->run();
}

1 // sharedApplication pointer
2 CCApplication * CCApplication::sm_pSharedApplication = 0;

1 CCApplication* CCApplication::sharedApplication()
2 {
3     CC_ASSERT(sm_pSharedApplication);
4     return sm_pSharedApplication;
5 }

 1 case WM_SIZE:
 2         switch (wParam)
 3         {
 4         case SIZE_RESTORED:
 5             CCApplication::sharedApplication()->applicationWillEnterForeground();
 6             break;
 7         case SIZE_MINIMIZED:
 8             CCApplication::sharedApplication()->applicationDidEnterBackground();
 9             break;
10         }
11         break;

1 int WINAPI WinMain(HINSTANCE hInstance,
2                    HINSTANCE hPreInstance,
3                    PSTR      szCmdLine,
4                    int       iCmdShow)
5 {
6     1）注册窗口类，并注册消息处理函数WindowProc
7     2）创建并显示窗口
8     3）循环获取消息
9 }

 1 LRESULT CALLBACK WindowProc(HWND   hwnd, 
 2                             UINT   uMsg,
 3                             WPARAM wParam,
 4                             LPARAM lParam)
 5 {
 6     switch (uMsg)
 7     {
 8         处理各种消息
 9     }
10 }

 1 int APIENTRY _tWinMain(HINSTANCE hInstance,
 2                        HINSTANCE hPrevInstance,
 3                        LPTSTR    lpCmdLine,
 4                        int       nCmdShow)
 5 {
 6     UNREFERENCED_PARAMETER(hPrevInstance);
 7     UNREFERENCED_PARAMETER(lpCmdLine);
 8 
 9     // create the application instance
10     AppDelegate app;
11 
12     // 以下代码对应Windows程序设计的一般框架
13     CCEGLView* eglView = CCEGLView::sharedOpenGLView();
14     eglView->setFrameSize(960, 640 );
15     return CCApplication::sharedApplication()->run();
16 }

1 CCEGLView* CCEGLView::sharedOpenGLView()
2 {
3     static CCEGLView* s_pEglView = NULL;
4     if (s_pEglView == NULL)
5     {
6         s_pEglView = new CCEGLView();
7     }
8     return s_pEglView;
9 }

1 void CCEGLView::setFrameSize(float width, float height)
2 {
3     Create((LPCTSTR)m_szViewName, (int)width, (int)height);
4     CCEGLViewProtocol::setFrameSize(width, height);
5 
6     resize(width, height); // adjust window size for menubar
7     centerWindow();
8 }

 1 bool CCEGLView::Create(LPCTSTR pTitle, int w, int h)
 2 {
 3     bool bRet = false;
 4     do 
 5     {
 6         CC_BREAK_IF(m_hWnd);
 7         // 创建窗口类
 8         HINSTANCE hInstance = GetModuleHandle( NULL );
 9         WNDCLASS  wc;        // Windows Class Structure
10 
11         // Redraw On Size, And Own DC For Window.
12         wc.style          = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;  
13         wc.lpfnWndProc    = _WindowProc;                    // WndProc Handles Messages
14         wc.cbClsExtra     = 0;                              // No Extra Window Data
15         wc.cbWndExtra     = 0;                              // No Extra Window Data
16         wc.hInstance      = hInstance;                      // Set The Instance
17         wc.hIcon          = LoadIcon( NULL, IDI_WINLOGO );  // Load The Default Icon
18         wc.hCursor        = LoadCursor( NULL, IDC_ARROW );  // Load The Arrow Pointer
19         wc.hbrBackground  = NULL;                           // No Background Required For GL
20         wc.lpszMenuName   = m_menu;                         // 
21         wc.lpszClassName  = kWindowClassName;               // Set The Class Name
22         // 注册窗口类
23         CC_BREAK_IF(! RegisterClass(&wc) && 1410 != GetLastError());        
24 
25         // center window position
26         RECT rcDesktop;
27         GetWindowRect(GetDesktopWindow(), &rcDesktop);
28 
29         WCHAR wszBuf[50] = {0};
30         MultiByteToWideChar(CP_UTF8, 0, m_szViewName, -1, wszBuf, sizeof(wszBuf));
31 
32         // 创建窗口(create window)
33         m_hWnd = CreateWindowEx(
34             WS_EX_APPWINDOW | WS_EX_WINDOWEDGE,                  // Extended Style For The Window
35             kWindowClassName,                                    // Class Name
36             wszBuf,                                              // Window Title
37             WS_CAPTION | WS_POPUPWINDOW | WS_MINIMIZEBOX,        // Defined Window Style
38             0, 0,                                                // Window Position
39             0,                                                   // Window Width
40             0,                                                   // Window Height
41             NULL,                                                // No Parent Window
42             NULL,                                                // No Menu
43             hInstance,                                           // Instance
44             NULL );
45 
46         CC_BREAK_IF(! m_hWnd);
47 
48         resize(w, h);
49 
50         bRet = initGL();
51         CC_BREAK_IF(!bRet);
52         
53         s_pMainWindow = this;
54         bRet = true;
55     } while (0);
56 
57     return bRet;
58 }

 1 static CCEGLView* s_pMainWindow = NULL;
 2 
 3 static LRESULT CALLBACK _WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 4 {
 5     if (s_pMainWindow && s_pMainWindow->getHWnd() == hWnd)
 6     {
 7         return s_pMainWindow->WindowProc(uMsg, wParam, lParam);
 8     }
 9     else
10     {
11         return DefWindowProc(hWnd, uMsg, wParam, lParam);
12     }
13 }

  1 LRESULT CCEGLView::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
  2 {
  3     BOOL bProcessed = FALSE;
  4 
  5     switch (message)
  6     {
  7     case WM_LBUTTONDOWN:
  8         if (m_pDelegate && MK_LBUTTON == wParam)
  9         {
 10             POINT point = {(short)LOWORD(lParam), (short)HIWORD(lParam)};
 11             CCPoint pt(point.x/CC_CONTENT_SCALE_FACTOR(), point.y/CC_CONTENT_SCALE_FACTOR());
 12             CCPoint tmp = ccp(pt.x, m_obScreenSize.height - pt.y);
 13             if (m_obViewPortRect.equals(CCRectZero) || m_obViewPortRect.containsPoint(tmp))
 14             {
 15                 m_bCaptured = true;
 16                 SetCapture(m_hWnd);
 17                 int id = 0;
 18                 pt.x *= m_windowTouchScaleX;
 19                 pt.y *= m_windowTouchScaleY;
 20                 handleTouchesBegin(1, &id, &pt.x, &pt.y);
 21             }
 22         }
 23         break;
 24 
 25     case WM_MOUSEMOVE:
 26         if (MK_LBUTTON == wParam && m_bCaptured)
 27         {
 28             POINT point = {(short)LOWORD(lParam), (short)HIWORD(lParam)};
 29             CCPoint pt(point.x/CC_CONTENT_SCALE_FACTOR(), point.y/CC_CONTENT_SCALE_FACTOR());
 30             int id = 0;
 31             pt.x *= m_windowTouchScaleX;
 32             pt.y *= m_windowTouchScaleY;
 33             handleTouchesMove(1, &id, &pt.x, &pt.y);
 34         }
 35         break;
 36 
 37     case WM_LBUTTONUP:
 38         if (m_bCaptured)
 39         {
 40             POINT point = {(short)LOWORD(lParam), (short)HIWORD(lParam)};
 41             CCPoint pt(point.x/CC_CONTENT_SCALE_FACTOR(), point.y/CC_CONTENT_SCALE_FACTOR());
 42             int id = 0;
 43             pt.x *= m_windowTouchScaleX;
 44             pt.y *= m_windowTouchScaleY;
 45             handleTouchesEnd(1, &id, &pt.x, &pt.y);
 46 
 47             ReleaseCapture();
 48             m_bCaptured = false;
 49         }
 50         break;
 51     case WM_SIZE:
 52         switch (wParam)
 53         {
 54         case SIZE_RESTORED:
 55             CCApplication::sharedApplication()->applicationWillEnterForeground();
 56             break;
 57         case SIZE_MINIMIZED:
 58             CCApplication::sharedApplication()->applicationDidEnterBackground();
 59             break;
 60         }
 61         break;
 62     case WM_KEYDOWN:
 63         if (wParam == VK_F1 || wParam == VK_F2)
 64         {
 65             CCDirector* pDirector = CCDirector::sharedDirector();
 66             if (GetKeyState(VK_LSHIFT) < 0 ||  GetKeyState(VK_RSHIFT) < 0 || GetKeyState(VK_SHIFT) < 0)
 67                 pDirector->getKeypadDispatcher()->dispatchKeypadMSG(wParam == VK_F1 ? kTypeBackClicked : kTypeMenuClicked);
 68         }
 69         if ( m_lpfnAccelerometerKeyHook!=NULL )
 70         {
 71             (*m_lpfnAccelerometerKeyHook)( message,wParam,lParam );
 72         }
 73         break;
 74     case WM_KEYUP:
 75         if ( m_lpfnAccelerometerKeyHook!=NULL )
 76         {
 77             (*m_lpfnAccelerometerKeyHook)( message,wParam,lParam );
 78         }
 79         break;
 80     case WM_CHAR:
 81         {
 82             if (wParam < 0x20)
 83             {
 84                 if (VK_BACK == wParam)
 85                 {
 86                     CCIMEDispatcher::sharedDispatcher()->dispatchDeleteBackward();
 87                 }
 88                 else if (VK_RETURN == wParam)
 89                 {
 90                     CCIMEDispatcher::sharedDispatcher()->dispatchInsertText("\n", 1);
 91                 }
 92                 else if (VK_TAB == wParam)
 93                 {
 94                     // tab input
 95                 }
 96                 else if (VK_ESCAPE == wParam)
 97                 {
 98                     // ESC input
 99                     //CCDirector::sharedDirector()->end();
100                 }
101             }
102             else if (wParam < 128)
103             {
104                 // ascii char
105                 CCIMEDispatcher::sharedDispatcher()->dispatchInsertText((const char *)&wParam, 1);
106             }
107             else
108             {
109                 char szUtf8[8] = {0};
110                 int nLen = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)&wParam, 1, szUtf8, sizeof(szUtf8), NULL, NULL);
111                 CCIMEDispatcher::sharedDispatcher()->dispatchInsertText(szUtf8, nLen);
112             }
113             if ( m_lpfnAccelerometerKeyHook!=NULL )
114             {
115                 (*m_lpfnAccelerometerKeyHook)( message,wParam,lParam );
116             }
117         }
118         break;
119     case WM_PAINT:
120         PAINTSTRUCT ps;
121         BeginPaint(m_hWnd, &ps);
122         EndPaint(m_hWnd, &ps);
123         break;
124 
125     case WM_CLOSE:
126         CCDirector::sharedDirector()->end();
127         break;
128 
129     case WM_DESTROY:
130         destroyGL();
131         PostQuitMessage(0);
132         break;
133 
134     default:
135         if (m_wndproc)
136         {
137             
138             m_wndproc(message, wParam, lParam, &bProcessed);
139             if (bProcessed) break;
140         }
141         return DefWindowProc(m_hWnd, message, wParam, lParam);
142     }
143 
144     if (m_wndproc && !bProcessed)
145     {
146         m_wndproc(message, wParam, lParam, &bProcessed);
147     }
148     return 0;
149 }

 1 LRESULT CCEGLView::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
 2 {
 3     switch (message)
 4     {
 5         // 处理各种消息
 6     }
 7     // 调用自定义的处理函数
 8     if (m_wndproc && !bProcessed)
 9     {
10         m_wndproc(message, wParam, lParam, &bProcessed);
11     }
12 
13     return 0;
14 }

1 return CCApplication::sharedApplication()->run();

 1 int CCApplication::run()
 2 {
 3     PVRFrameEnableControlWindow(false);
 4 
 5     // Main message loop:
 6     MSG msg;
 7     LARGE_INTEGER nFreq;
 8     LARGE_INTEGER nLast;
 9     LARGE_INTEGER nNow;
10 
11     QueryPerformanceFrequency(&nFreq);
12     QueryPerformanceCounter(&nLast);
13 
14     // Initialize instance and cocos2d.
15     if (!applicationDidFinishLaunching())
16     {
17         return 0;
18     }
19 
20     CCEGLView* pMainWnd = CCEGLView::sharedOpenGLView();
21     pMainWnd->centerWindow();
22     ShowWindow(pMainWnd->getHWnd(), SW_SHOW);
23 
24     while (1)
25     {
26         if (! PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
27         {
28             // Get current time tick.
29             QueryPerformanceCounter(&nNow);
30 
31             // If it's the time to draw next frame, draw it, else sleep a while.
32             if (nNow.QuadPart - nLast.QuadPart > m_nAnimationInterval.QuadPart)
33             {
34                 nLast.QuadPart = nNow.QuadPart;
35                 CCDirector::sharedDirector()->mainLoop();
36             }
37             else
38             {
39                 Sleep(0);
40             }
41             continue;
42         }
43 
44         if (WM_QUIT == msg.message)
45         {
46             // Quit message loop.
47             break;
48         }
49 
50         // Deal with windows message.
51         if (! m_hAccelTable || ! TranslateAccelerator(msg.hwnd, m_hAccelTable, &msg))
52         {
53             TranslateMessage(&msg);
54             DispatchMessage(&msg);
55         }
56     }
57 
58     return (int) msg.wParam;
59 }

 1 int CCApplication::run()
 2 {
 3     // 显示窗口
 4     CCEGLView* pMainWnd = CCEGLView::sharedOpenGLView();
 5     pMainWnd->centerWindow();
 6     ShowWindow(pMainWnd->getHWnd(), SW_SHOW);
 7 
 8     while (1)
 9     {
10         if (! PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
11         {
12             // 处理一些数据
13             continue;
14         }
15 
16         if (WM_QUIT == msg.message)
17         {
18             // 退出消息循环(Quit message loop)
19             break;
20         }
21 
22         // 处理快捷键
23     }
24 
25     return (int) msg.wParam;
26 }

 1 class  AppDelegate : private cocos2d::CCApplication
 2 {
 3 public:
 4     AppDelegate();
 5     virtual ~AppDelegate();
 6 
 7     /**
 8     @brief    Implement CCDirector and CCScene init code here.
 9     @return true    Initialize success, app continue.
10     @return false   Initialize failed, app terminate.
11     */
12     virtual bool applicationDidFinishLaunching();
13 
14     /**
15     @brief  The function be called when the application enter background
16     @param  the pointer of the application
17     */
18     virtual void applicationDidEnterBackground();
19 
20     /**
21     @brief  The function be called when the application enter foreground
22     @param  the pointer of the application
23     */
24     virtual void applicationWillEnterForeground();
25 };

 1 bool AppDelegate::applicationDidFinishLaunching()
 2 {
 3     // initialize director
 4     CCDirector *pDirector = CCDirector::sharedDirector();
 5 
 6     pDirector->setOpenGLView(CCEGLView::sharedOpenGLView());
 7     
 8     TargetPlatform target = getTargetPlatform();
 9     
10     if (target == kTargetIpad)
11     {
12         // ipad
13         CCFileUtils::sharedFileUtils()->setResourceDirectory("iphonehd");
14         
15         // don't enable retina because we don't have ipad hd resource
16         CCEGLView::sharedOpenGLView()->setDesignResolutionSize(960, 640, kResolutionNoBorder);
17     }
18     else if (target == kTargetIphone)
19     {
20         // iphone
21         
22         // try to enable retina on device
23         if (true == CCDirector::sharedDirector()->enableRetinaDisplay(true))
24         {
25             // iphone hd
26             CCFileUtils::sharedFileUtils()->setResourceDirectory("iphonehd");
27         }
28         else 
29         {
30             CCFileUtils::sharedFileUtils()->setResourceDirectory("iphone");
31         }
32     }
33     else 
34     {
35         // android, windows, blackberry, linux or mac
36         // use 960*640 resources as design resolution size
37         CCFileUtils::sharedFileUtils()->setResourceDirectory("iphonehd");
38         CCEGLView::sharedOpenGLView()->setDesignResolutionSize(960, 640, kResolutionNoBorder);
39     }
40 
41     // turn on display FPS
42     pDirector->setDisplayStats(true);
43 
44     // set FPS. the default value is 1.0/60 if you don't call this
45     pDirector->setAnimationInterval(1.0 / 60);
46 
47     // create a scene. it's an autorelease object
48     CCScene *pScene = HelloWorld::scene();
49 
50     // run
51     pDirector->runWithScene(pScene);
52 
53     return true;
54 }

 1 // This function will be called when the app is inactive. When comes a phone call,it's be invoked too
 2 void AppDelegate::applicationDidEnterBackground() 
 3 {
 4     CCDirector::sharedDirector()->stopAnimation();
 5 
 6     // if you use SimpleAudioEngine, it must be pause
 7     // SimpleAudioEngine::sharedEngine()->pauseBackgroundMusic();
 8 }
 9 
10 // this function will be called when the app is active again
11 void AppDelegate::applicationWillEnterForeground() 
12 {
13     CCDirector::sharedDirector()->startAnimation();
14 
15     // if you use SimpleAudioEngine, it must resume here
16     // SimpleAudioEngine::sharedEngine()->resumeBackgroundMusic();
17 }

如注释所陈述的，applicationDidEnterBackground函数会在程序进入“非活跃”状态（即失去窗口焦点）时被调用，而applicationWillEnterForeground函数会在程序进入“活跃”状态（即获得窗口焦点）时被调用（可以自己在这个函数里面下断点看看具体执行的流程）。

舞台需要场景

演员站在舞台上，却表演于场景中

                                —— by 我挂科了

赋词一句略显文艺范儿，求勿喷！言归正传，首先我们来看看HelloWorld的继承关系

HelloWorld从CCLayer继承，而CCLayer又是一个非常复杂的（至少它的father太多了）。你一定觉得HelloWorld很复杂吧，其实它没有传说中那么复杂

 1 class HelloWorld : public cocos2d::CCLayer
 2 {
 3 public:
 4     // Here's a difference. Method 'init' in cocos2d-x returns bool, instead of returning 'id' in cocos2d-iphone
 5     virtual bool init();  
 6 
 7     // there's no 'id' in cpp, so we recommend returning the class instance pointer
 8     static cocos2d::CCScene* scene();
 9     
10     // a selector callback
11     void menuCloseCallback(CCObject* pSender);
12 
13     // touch callback
14     void ccTouchesBegan(cocos2d::CCSet *pTouches, cocos2d::CCEvent *pEvent);
15     
16     // implement the "static node()" method manually
17     CREATE_FUNC(HelloWorld);
18 };

多么单纯的类啊！你也许会说：CREATE_FUNC是神马东东？它一点都不单纯啊~  

3.1、CREATE_FUNC

其实HelloWorld还是很单纯的，因为CREATE_FUNC定义很简单

 1 #define CREATE_FUNC(__TYPE__) \
 2 static __TYPE__* create() \
 3 { \
 4     __TYPE__ *pRet = new __TYPE__(); \
 5     if (pRet && pRet->init()) \
 6     { \
 7         pRet->autorelease(); \
 8         return pRet; \
 9     } \
10     else \
11     { \
12         delete pRet; \
13         pRet = NULL; \
14         return NULL; \
15     } \
16 }

CREATE_FUNC是一个宏，它定义了一个名为create的static函数，该函数完成下面几个事情：

1）创建__TYPE__类型的对象指针

2）如果创建成功，则调用该对象的init函数

a）如果init函数执行成功，则调用该对象的autorelease函数并返回该对象指针

b）如果init函数执行失败，则释放该对象并返回NULL

将这个宏在HelloWorld类中展开，HelloWorld就露出了它的真面目了

 1 class HelloWorld : public cocos2d::CCLayer
 2 {
 3 public:
 4     // Here's a difference. Method 'init' in cocos2d-x returns bool, instead of returning 'id' in cocos2d-iphone
 5     virtual bool init();  
 6 
 7     // there's no 'id' in cpp, so we recommend returning the class instance pointer
 8     static cocos2d::CCScene* scene();
 9     
10     // a selector callback
11     void menuCloseCallback(CCObject* pSender);
12 
13     // touch callback
14     void ccTouchesBegan(cocos2d::CCSet *pTouches, cocos2d::CCEvent *pEvent);
15     
16     // implement the "static node()" method manually
17     static HelloWorld* create() 
18     { 
19         HelloWorld *pRet = new HelloWorld(); 
20         if (pRet && pRet->init()) 
21         { 
22             pRet->autorelease(); 
23             return pRet; 
24         } 
25         else 
26         { 
27             delete pRet; 
28             pRet = NULL; 
29             return NULL; 
30         } 
31     }
32 };

我比较奇怪的是，为什么注释上写的是“static node()”而不是“static create()”呢？隐约听到有人在喊：这一定是笔误！好吧，不要在意这些细节。

3.2  梦回AppDelegate

还记得AppDelegate::applicationDidFinishLauching函数吗？它的实现中有这么一句

 1 bool AppDelegate::applicationDidFinishLaunching() 
 2 {
 3     // 其他操作
 4 
 5     // create a scene. it's an autorelease object
 6     CCScene *pScene = HelloWorld::scene();
 7     // run
 8     pDirector->runWithScene(pScene);
 9 
10     // 其他操作
11 }

这是我们的HelloWorld第一次在程序中被使用，那我们就从HelloWorld::scene函数入手吧

 1 CCScene* HelloWorld::scene()
 2 {
 3     // 'scene' is an autorelease object
 4     CCScene *scene = CCScene::create();
 5     
 6     // 'layer' is an autorelease object
 7     HelloWorld *layer = HelloWorld::create();
 8 
 9     // add layer as a child to scene
10     scene->addChild(layer);
11 
12     // return the scene
13     return scene;
14 }

这个函数的实现完成了3个事情：

1）创建了一个空的CCScene对象scene

2）通过上面分析过的HelloWorld::create函数创建了一个HelloWorld对象layer，并将layer作为scene的一个子节点添加到scene中

3）将scene返回

3.3  初始化

在前面我们已经展示了HelloWorld::create函数，它创建了HelloWorld对象后会调用该对象的init函数来初始化对象。HelloWorld::init函数实现如下

 1 // on "init" you need to initialize your instance
 2 bool HelloWorld::init()
 3 {
 4     //
 5     // 1. super init first
 6     if ( !CCLayer::init() )
 7     {
 8         return false;
 9     }
10     
11     CCSize visibleSize = CCDirector::sharedDirector()->getVisibleSize();
12     CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();
13 
14     /////
15     // 2. add a menu item with "X" image, which is clicked to quit the program
16     //    you may modify it.
17 
18     // add a "close" icon to exit the progress. it's an autorelease object
19     CCMenuItemImage *pCloseItem = CCMenuItemImage::create(
20                                         "CloseNormal.png",
21                                         "CloseSelected.png",
22                                         this,
23                                         menu_selector(HelloWorld::menuCloseCallback));
24     pCloseItem->setPosition(ccp(origin.x + visibleSize.width - pCloseItem->getContentSize().width/2 ,
25                                 origin.y + pCloseItem->getContentSize().height/2));
26     // create menu, it's an autorelease object
27     CCMenu* pMenu = CCMenu::create(pCloseItem, NULL);
28     pMenu->setPosition(CCPointZero);
29     this->addChild(pMenu, 1);
30 
31     /////
32     // 3. add your codes below...
33 
34     // add a label shows "Hello World"
35     // create and initialize a label
36     CCLabelTTF* pLabel = CCLabelTTF::create("Hello World", "Arial", 24);
37     // position the label on the center of the screen
38     pLabel->setPosition(ccp(origin.x + visibleSize.width/2,
39                             origin.y + visibleSize.height - pLabel->getContentSize().height));
40     // add the label as a child to this layer
41     this->addChild(pLabel, 1);
42 
43     // add "HelloWorld" splash screen"
44     CCSprite* pSprite = CCSprite::create("HelloWorld.png");
45     // position the sprite on the center of the screen
46     pSprite->setPosition(ccp(visibleSize.width/2 + origin.x, visibleSize.height/2 + origin.y));
47     // add the sprite as a child to this layer
48     this->addChild(pSprite, 0);
49     
50     // enable standard touch
51     this->setTouchEnabled(true);
52     
53     return true;
54 }

不要看这个函数很长，实际上主要完成了4个事情

1）调用父类的初始化函数（CCLayer::init())完成对继承自父类成员的初始化

2）创建一个菜单（CCMenu）并在其中添加一个菜单项（CCMenuItem），将菜单显示在HelloWorld中。点击这个菜单项可以关闭程序

3）创建一个标签（CCLabel），让它在HelloWorld中显示“HelloWorld”字串

4）创建一个精灵（CCSprite），让它在HelloWorld中显示图片“HelloWorld.png”

HelloWorld::init函数中所创建的都是我们在运行起来的界面中所能看到的东西，这其中涉及到一些类将在后面学习，这里不深究。我比较好奇的是菜单项所实现的功能：点击后关闭程序（不信你亲自点一下试试）。这是怎么实现的呢？仔细分析一下菜单项的创建过程

1 // add a "close" icon to exit the progress. it's an autorelease object
2 CCMenuItemImage *pCloseItem = CCMenuItemImage::create(
3                                     "CloseNormal.png",
4                                     "CloseSelected.png",
5                                     this,
6                                     menu_selector(HelloWorld::menuCloseCallback));

最后一个参数形式很特别啊~ 我们先看看menu_selector是神马东西

1 #define menu_selector(_SELECTOR) (SEL_MenuHandler)(&_SELECTOR)

又是一个宏！它所完成的事情是将_SELECTOR取址并强制转换为SEL_MenuHandler类型。那么SEL_MenuHandler又是什么类型呢？

1 typedef void (CCObject::*SEL_MenuHandler)(CCObject*);

它是一个函数指针，这类函数有一个CCObject*类型的参数。此时我们可以将创建菜单项的代码展开，看看其真实的原貌

1 // add a "close" icon to exit the progress. it's an autorelease object
2 CCMenuItemImage *pCloseItem = CCMenuItemImage::create(
3                                     "CloseNormal.png",
4                                     "CloseSelected.png",
5                                     this,
6                                     (SEL_MenuHandler)&HelloWorld::menuCloseCallback);

HelloWorld::menuCloseCallback函数以回调函数的方式传入菜单项，在点击菜单项时被触发。也就是说实现关闭程序功能的是HelloWorld::menuCloseCallback函数

1 void HelloWorld::menuCloseCallback(CCObject* pSender)
2 {
3     CCDirector::sharedDirector()->end();
4 
5 #if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
6     exit(0);
7 #endif
8 }

最终，由CCDirector::end函数完成程序的关闭（在IOS中还需要调用exit函数）。

参考文献 

Cocos2d-x 高级开发教程：制作自己的捕鱼达人