我的Cocos2d-x学习笔记（二）AppDelegate补充介绍

概述    上一篇中只介绍AppDelegate中applicationDidFinishLaunching()函数，这个函数是程序运行的关键，在CCApplicationProtocol中声明纯虚函数，在CCApplication中进行调用。在CCApplicationProtocol中与applicationDidFinishLaunching()类似的纯虚函数还有两个，分别是：applicati

上一篇中只介绍AppDelegate中applicationDIDFinishLaunching()函数，这个函数是程序运行的关键，在CCApplicationProtocol中声明纯虚函数，在CCApplication中进行调用。在CCApplicationProtocol中与applicationDIDFinishLaunching()类似的纯虚函数还有两个，分别是：applicationDIDEnterBackground()和applicationWillEnterForeground()，在CCApplicationProtocol中声明如下：

class CC_DLL CCApplicationProtocol{public:	/**	@brIEf    Implement CCDirector and CCScene init code here.	@return true    Initialize success,app continue.	@return false   Initialize Failed,app terminate.	*/	virtual bool applicationDIDFinishLaunching() = 0;	/**	@brIEf  The function be called when the application enter background	@param  the pointer of the application	*/	virtual voID applicationDIDEnterBackground() = 0;	/**	@brIEf  The function be called when the application enter foreground	@param  the pointer of the application	*/	virtual voID applicationWillEnterForeground() = 0;}

在AppDelegate对其中类成员函数进行覆写，AppDelegate.h中的代码如下：

#ifndef  _APP_DELEGATE_H_#define  _APP_DELEGATE_H_#include "cocos2d.h"/**@brIEf    The cocos2d Application.The reason for implement as private inheritance is to hIDe some interface call by CCDirector.*/class  AppDelegate : private cocos2d::CCApplication{public:    AppDelegate();    virtual ~AppDelegate();    /**    @brIEf    Implement CCDirector and CCScene init code here.    @return true    Initialize success,app continue.    @return false   Initialize Failed,app terminate.    */    virtual bool applicationDIDFinishLaunching();    /**    @brIEf  The function be called when the application enter background    @param  the pointer of the application    */    virtual voID applicationDIDEnterBackground();    /**    @brIEf  The function be called when the application enter foreground    @param  the pointer of the application    */    virtual voID applicationWillEnterForeground();};#endif // _APP_DELEGATE_H_

由官方的注释就可知道applicationDIDEnterBackground()和applicationWillEnterForeground()的作用，applicationDIDEnterBackground()函数是游戏程序进入后台运行时候调用的，applicationWillEnterForeground()函数是游戏程序从后台恢复到前台运行时候调用的。
再来看看AppDelegate.cpp中的内容，代码如下：

#include "AppDelegate.h"USING_NS_CC;AppDelegate::AppDelegate() {}AppDelegate::~AppDelegate() {}bool AppDelegate::applicationDIDFinishLaunching() {    // initialize director    CCDirector* pDirector = CCDirector::sharedDirector();    CCEGLVIEw* pEGLVIEw = CCEGLVIEw::sharedOpenGLVIEw();    pDirector->setopenGLVIEw(pEGLVIEw);	    // turn on display FPS    pDirector->setdisplayStats(true);    // set FPS. the default value is 1.0/60 if you don't call this    pDirector->setAnimationInterval(1.0 / 60);	CCScene *pScene = HelloWorld::scene();    // run    pDirector->runWithScene(pScene);    return true;}// This function will be called when the app is inactive. When comes a phone call,it's be invoked toovoID AppDelegate::applicationDIDEnterBackground() {    CCDirector::sharedDirector()->stopAnimation();    // if you use SimpleAudioEngine,it must be pause    // SimpleAudioEngine::sharedEngine()->pauseBackgroundMusic();}// this function will be called when the app is active againvoID AppDelegate::applicationWillEnterForeground() {    CCDirector::sharedDirector()->startAnimation();    // if you use SimpleAudioEngine,it must resume here    // SimpleAudioEngine::sharedEngine()->resumeBackgroundMusic();}

AppDelegate的构造函数与析构函数是空的，构造函数运行时候通过执行父类构造函数初始化CCApplication单例对象，之后没有其他功能。

CCDirector* pDirector = CCDirector::sharedDirector();得到了一个CCDirector单例对象并把指针赋值给pDirector 。
CCEGLVIEw* pEGLVIEw = CCEGLVIEw::sharedOpenGLVIEw();Cocos2d-x对OpenGL进行了封装，Cocos2d-x对OpenGL进行了初始化。
pDirector->setopenGLVIEw(pEGLVIEw); 设置了场景的窗口。

pDirector->setdisplayStats(true);启用FPS显示，设置是否显示游戏的帧数等调试信息。

pDirector->setAnimationInterval(1.0 / 60);设置游戏的帧率，即每秒刷新画面次数，这里是60帧每秒。

其中重点关注以下两句：

CCScene *pScene = HelloWorld::scene();    // run    pDirector->runWithScene(pScene);

上面的第一句：CCScene *pScene = HelloWorld::scene();创建了一个场景，这个场景就是HelloWorld，然后把这个场景指针赋值给pScene，之后通过pDirector->runWithScene(pScene);把这个HelloWorld场景运行起来。我们需要知道的是pDirector是一个CCDirector单例对象的指针，CCDirector是控制游戏中各种元素的类。

总结一下：CCApplicationProtocol中定义了运行时用到的几个接口，前台运行、进入后台运行、返回前台运行三个接口；CCApplication中包装了跨平台的实现；AppDelegate 则具体实现了CCApplicationProtocol定义的各个接口。

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