Android cocos2dx游戏开发——示例程序HelloCpp源码分析

      我们从HelloCpp.java开始：

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1. package org.cocos2dx.hellocpp;  
2.   
3. import org.cocos2dx.lib.Cocos2dxActivity;  
4.   
5. import android.os.Bundle;  
6.   
7. public class HelloCpp extends Cocos2dxActivity{  
8.   
9.     protected void onCreate(Bundle savedInstanceState){  
10.         super.onCreate(savedInstanceState);  
11.     }  
12.       
13.     static {  
14.          System.loadLibrary("hellocpp");  
15.     }  
16. }  

package org.cocos2dx.hellocpp;

import org.cocos2dx.lib.Cocos2dxActivity;

import android.os.Bundle;

public class HelloCpp extends Cocos2dxActivity{

	protected void onCreate(Bundle savedInstanceState){
		super.onCreate(savedInstanceState);
	}
	
    static {
         System.loadLibrary("hellocpp");
    }
}

      HelloCpp是一个Activity，首先会执行静态代码块，加载libhellocpp.so库，然后就是执行onCreate方法，这里调用了父类的onCreate方法。我们看看Cocos2dxActivity的onCreate方法，该类在cocos2dx的库工程libcocos2dx中：

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1. @Override  
2.     protected void onCreate(final Bundle savedInstanceState) {  
3.         super.onCreate(savedInstanceState);  
4.         sContext = this;  
5.         this.mHandler = new Cocos2dxHandler(this);  
6.   
7.         this.init();  
8.   
9.         Cocos2dxHelper.init(this, this);  
10.     }  

@Override
	protected void onCreate(final Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		sContext = this;
    	this.mHandler = new Cocos2dxHandler(this);

    	this.init();

		Cocos2dxHelper.init(this, this);
	}

      这里主要是执行初始化过程，Cocos2dxHandler主要处理显示Dialog的消息，Cocos2dxHelper是个辅助类，我们主要看init()方法：

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1. public void init() {  
2.           
3.         // FrameLayout  
4.         ViewGroup.LayoutParams framelayout_params =  
5.             new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,  
6.                                        ViewGroup.LayoutParams.FILL_PARENT);  
7.         FrameLayout framelayout = new FrameLayout(this);  
8.         framelayout.setLayoutParams(framelayout_params);  
9.   
10.         // Cocos2dxEditText layout  
11.         ViewGroup.LayoutParams edittext_layout_params =  
12.             new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,  
13.                                        ViewGroup.LayoutParams.WRAP_CONTENT);  
14.         Cocos2dxEditText edittext = new Cocos2dxEditText(this);  
15.         edittext.setLayoutParams(edittext_layout_params);  
16.   
17.         // ...add to FrameLayout  
18.         framelayout.addView(edittext);  
19.   
20.         // Cocos2dxGLSurfaceView  
21.         this.mGLSurfaceView = this.onCreateView();  
22.   
23.         // ...add to FrameLayout  
24.         framelayout.addView(this.mGLSurfaceView);  
25.   
26.         // Switch to supported OpenGL (ARGB888) mode on emulator  
27.         if (isAndroidEmulator())  
28.            this.mGLSurfaceView.setEGLConfigChooser(8 , 8, 8, 8, 16, 0);  
29.   
30.         this.mGLSurfaceView.setCocos2dxRenderer(new Cocos2dxRenderer());  
31.         this.mGLSurfaceView.setCocos2dxEditText(edittext);  
32.   
33.         // Set framelayout as the content view  
34.         setContentView(framelayout);  
35.     }  

public void init() {
		
    	// FrameLayout
        ViewGroup.LayoutParams framelayout_params =
            new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
                                       ViewGroup.LayoutParams.FILL_PARENT);
        FrameLayout framelayout = new FrameLayout(this);
        framelayout.setLayoutParams(framelayout_params);

        // Cocos2dxEditText layout
        ViewGroup.LayoutParams edittext_layout_params =
            new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,
                                       ViewGroup.LayoutParams.WRAP_CONTENT);
        Cocos2dxEditText edittext = new Cocos2dxEditText(this);
        edittext.setLayoutParams(edittext_layout_params);

        // ...add to FrameLayout
        framelayout.addView(edittext);

        // Cocos2dxGLSurfaceView
        this.mGLSurfaceView = this.onCreateView();

        // ...add to FrameLayout
        framelayout.addView(this.mGLSurfaceView);

        // Switch to supported OpenGL (ARGB888) mode on emulator
        if (isAndroidEmulator())
           this.mGLSurfaceView.setEGLConfigChooser(8 , 8, 8, 8, 16, 0);

        this.mGLSurfaceView.setCocos2dxRenderer(new Cocos2dxRenderer());
        this.mGLSurfaceView.setCocos2dxEditText(edittext);

        // Set framelayout as the content view
		setContentView(framelayout);
	}

      这里就是为Activity绑定View Hierarchy，大家做Android开发的对着一定很熟悉。View Hierarchy的根View是个FrameLayout，FrameLayout又包含一个EditText和一个GLSurfaceView，这个GLSurfaceView就是cocos引擎用来绘制游戏画面的关键View，我们来详细分析一下它。首先看一下Cocos2dxActivity的onCreateView方法：

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1. public Cocos2dxGLSurfaceView onCreateView() {  
2.         return new Cocos2dxGLSurfaceView(this);  
3.     }  

public Cocos2dxGLSurfaceView onCreateView() {
    	return new Cocos2dxGLSurfaceView(this);
    }

      该方法就是新建一个Cocos2dxGLSurfaceView，Cocos2dxGLSurfaceView又继承于GLSurfaceView。我们都知道GLSurfaceView的核心就是Renderer，初始化时会调用Renderer的onSurfaceCreated方法，每一帧的绘制是通过调用Renderer的onDrawFrame方法。Cocos2dxGLSurfaceView的Renderer是一个Cocos2dxRenderer对象，我们先来看Cocos2dxRenderer对象的onSurfaceCreated方法：

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1. @Override  
2.     public void onSurfaceCreated(final GL10 pGL10, final EGLConfig pEGLConfig) {  
3.         Cocos2dxRenderer.nativeInit(this.mScreenWidth, this.mScreenHeight);  
4.         this.mLastTickInNanoSeconds = System.nanoTime();  
5.     }  

@Override
	public void onSurfaceCreated(final GL10 pGL10, final EGLConfig pEGLConfig) {
		Cocos2dxRenderer.nativeInit(this.mScreenWidth, this.mScreenHeight);
		this.mLastTickInNanoSeconds = System.nanoTime();
	}

      这里调用了一个本地方法nativeInit(final int pWidth, final int pHeight)，本地方法的实现在jni/hellocpp/main.cpp中实现的：

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1. void Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeInit(JNIEnv*  env, jobject thiz, jint w, jint h)  
2. {  
3.     if (!CCDirector::sharedDirector()->getOpenGLView())  
4.     {  
5.         CCEGLView *view = CCEGLView::sharedOpenGLView();  
6.         view->setFrameSize(w, h);  
7.   
8.         AppDelegate *pAppDelegate = new AppDelegate();  
9.         CCApplication::sharedApplication()->run();  
10.     }  
11.     else  
12.     {  
13.         ......   
14.     }  
15. }  

void Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeInit(JNIEnv*  env, jobject thiz, jint w, jint h)
{
    if (!CCDirector::sharedDirector()->getOpenGLView())
    {
        CCEGLView *view = CCEGLView::sharedOpenGLView();
        view->setFrameSize(w, h);

        AppDelegate *pAppDelegate = new AppDelegate();
        CCApplication::sharedApplication()->run();
    }
    else
    {
        ...... 
    }
}

      CCDirector是游戏的导演类，一个游戏只有一个导演类用来控制和管理场景。CCDirector::sharedDirector()是个静态方法，用来获取导演类的单例对象：

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1. CCDirector* CCDirector::sharedDirector(void)  
2. {  
3.     if (!s_SharedDirector)  
4.     {  
5.         s_SharedDirector = new CCDisplayLinkDirector();  
6.         s_SharedDirector->init();  
7.     }  
8.   
9.     return s_SharedDirector;  
10. }  

CCDirector* CCDirector::sharedDirector(void)
{
    if (!s_SharedDirector)
    {
        s_SharedDirector = new CCDisplayLinkDirector();
        s_SharedDirector->init();
    }

    return s_SharedDirector;
}

      CCCCDisplayLinkDirector是CCDirector的子类。我们再回到nativeinit方法中，获取到导演类的单例对象后又调用了它的getOpenGLView()方法：

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1. inline CCEGLView* getOpenGLView(void) { return m_pobOpenGLView; }  

inline CCEGLView* getOpenGLView(void) { return m_pobOpenGLView; }

      该方法返回用于游戏绘制的CCEGLView，在Android平台下，这个CCEGLView其实没有什么作用，因为游戏都是绘制在Cocos2dxGLSurfaceView上的。由于我们是初始化过程，所以此时m_pobOpenGLView为null，所以if (!CCDirector::sharedDirector()->getOpenGLView())条件成立，执行以下的代码：

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1. CCEGLView *view = CCEGLView::sharedOpenGLView();  
2. view->setFrameSize(w, h);  
3.   
4. AppDelegate *pAppDelegate = new AppDelegate();  
5. CCApplication::sharedApplication()->run();  

   CCEGLView *view = CCEGLView::sharedOpenGLView();
   view->setFrameSize(w, h);

   AppDelegate *pAppDelegate = new AppDelegate();
   CCApplication::sharedApplication()->run();

     同样，我们先获取一个CCEGLView的单例对象，接下来又新建了一个AppDelegate对象，大家可能在工程中找不到AppDelegate类。我们打开工程目录的上一级目录：
      我们的Android工程是在proj.android文件夹中，而AppDelegate类就在Classes文件夹中。因为cocos2dx是跨平台的，而AppDelegate在各个平台之间是通用的不需要修改的，所以就放在一个公用的目录下。

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1. #ifndef  _APP_DELEGATE_H_  
2. #define  _APP_DELEGATE_H_  
3.   
4. #include "cocos2d.h"  
5.   
6. /** 
7. @brief    The cocos2d Application. 
8.  
9. The reason for implement as private inheritance is to hide some interface call by CCDirector. 
10. */  
11. class  AppDelegate : private cocos2d::CCApplication  
12. {  
13. public:  
14.     AppDelegate();  
15.     virtual ~AppDelegate();  
16.   
17.     /** 
18.     @brief    Implement CCDirector and CCScene init code here. 
19.     @return true    Initialize success, app continue. 
20.     @return false   Initialize failed, app terminate. 
21.     */  
22.     virtual bool applicationDidFinishLaunching();  
23.   
24.     /** 
25.     @brief  The function be called when the application enter background 
26.     @param  the pointer of the application 
27.     */  
28.     virtual void applicationDidEnterBackground();  
29.   
30.     /** 
31.     @brief  The function be called when the application enter foreground 
32.     @param  the pointer of the application 
33.     */  
34.     virtual void applicationWillEnterForeground();  
35. };  
36.   
37. #endif // _APP_DELEGATE_H_  

#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_

     AppDelegate是继承CCApplication类的，我们看一下CCApplication的构造方法：

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1. // sharedApplication pointer  
2. CCApplication * CCApplication::sm_pSharedApplication = 0;  
3.   
4. CCApplication::CCApplication()  
5. {  
6.     CCAssert(! sm_pSharedApplication, "");  
7.     sm_pSharedApplication = this;  
8. }  

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

CCApplication::CCApplication()
{
    CCAssert(! sm_pSharedApplication, "");
    sm_pSharedApplication = this;
}

      我们看到在新建CCApplication对象时，会把该对象赋给一个全局变量sm_pSharedApplication。所以我们在new AppDelegate()的时候，就把它象赋给全局变量sm_pSharedApplication。我们再看下CCApplication的CCApplication::sharedApplication方法：

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1. CCApplication* CCApplication::sharedApplication()  
2. {  
3.     CCAssert(sm_pSharedApplication, "");  
4.     return sm_pSharedApplication;  
5. }  

CCApplication* CCApplication::sharedApplication()
{
    CCAssert(sm_pSharedApplication, "");
    return sm_pSharedApplication;
}

      此时，sm_pSharedApplication指向的是一个AppDelegate对象。所以我们执行CCApplication::sharedApplication()->run()时其实执行的是AppDelegate对象的run方法。现在我们应该明白这个类为什么叫AppDelegate了，因为CCApplication的工作实际都委托给了AppDelegate类了。看一下AppDelegate的方法：

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1. int CCApplication::run()  
2. {  
3.     // Initialize instance and cocos2d.  
4.     if (! applicationDidFinishLaunching())  
5.     {  
6.         return 0;  
7.     }  
8.       
9.     return -1;  
10. }  

int CCApplication::run()
{
    // Initialize instance and cocos2d.
    if (! applicationDidFinishLaunching())
    {
        return 0;
    }
    
    return -1;
}

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1. bool AppDelegate::applicationDidFinishLaunching() {  
2.     // initialize director  
3.     CCDirector* pDirector = CCDirector::sharedDirector();  
4.     CCEGLView* pEGLView = CCEGLView::sharedOpenGLView();  
5.   
6.     pDirector->setOpenGLView(pEGLView);  
7.     CCSize frameSize = pEGLView->getFrameSize();  
8.   
9.     // Set the design resolution  
10. #if (CC_TARGET_PLATFORM == CC_PLATFORM_WINRT) || (CC_TARGET_PLATFORM == CC_PLATFORM_WP8)  
11.     pEGLView->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, kResolutionShowAll);  
12. #else  
13.     pEGLView->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, kResolutionNoBorder);  
14. #endif  
15.   
16.       
17.     vector<string> searchPath;  
18.   
19.     // In this demo, we select resource according to the frame‘s height.  
20.     // If the resource size is different from design resolution size, you need to set contentScaleFactor.  
21.     // We use the ratio of resource‘s height to the height of design resolution,  
22.     // this can make sure that the resource‘s height could fit for the height of design resolution.  
23.   
24.     // if the frame‘s height is larger than the height of medium resource size, select large resource.  
25.     if (frameSize.height > mediumResource.size.height)  
26.     {  
27.         searchPath.push_back(largeResource.directory);  
28.   
29.         pDirector->setContentScaleFactor(MIN(largeResource.size.height/designResolutionSize.height, largeResource.size.width/designResolutionSize.width));  
30.     }  
31.     // if the frame‘s height is larger than the height of small resource size, select medium resource.  
32.     else if (frameSize.height > smallResource.size.height)  
33.     {  
34.         searchPath.push_back(mediumResource.directory);  
35.           
36.         pDirector->setContentScaleFactor(MIN(mediumResource.size.height/designResolutionSize.height, mediumResource.size.width/designResolutionSize.width));  
37.     }  
38.     // if the frame‘s height is smaller than the height of medium resource size, select small resource.  
39.     else  
40.     {  
41.         searchPath.push_back(smallResource.directory);  
42.   
43.         pDirector->setContentScaleFactor(MIN(smallResource.size.height/designResolutionSize.height, smallResource.size.width/designResolutionSize.width));  
44.     }  
45.   
46.   
47.     // set searching path  
48.     CCFileUtils::sharedFileUtils()->setSearchPaths(searchPath);  
49.       
50.     // turn on display FPS  
51.     pDirector->setDisplayStats(true);  
52.   
53.     // set FPS. the default value is 1.0/60 if you don‘t call this  
54.     pDirector->setAnimationInterval(1.0 / 60);  
55.   
56.     // create a scene. it‘s an autorelease object  
57.     CCScene *pScene = HelloWorld::scene();  
58.   
59.     // run  
60.     pDirector->runWithScene(pScene);  
61.   
62.     return true;  
63. }  

bool AppDelegate::applicationDidFinishLaunching() {
    // initialize director
    CCDirector* pDirector = CCDirector::sharedDirector();
    CCEGLView* pEGLView = CCEGLView::sharedOpenGLView();

    pDirector->setOpenGLView(pEGLView);
	CCSize frameSize = pEGLView->getFrameSize();

    // Set the design resolution
#if (CC_TARGET_PLATFORM == CC_PLATFORM_WINRT) || (CC_TARGET_PLATFORM == CC_PLATFORM_WP8)
    pEGLView->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, kResolutionShowAll);
#else
    pEGLView->setDesignResolutionSize(designResolutionSize.width, designResolutionSize.height, kResolutionNoBorder);
#endif

    
    vector<string> searchPath;

    // In this demo, we select resource according to the frame's height.
    // If the resource size is different from design resolution size, you need to set contentScaleFactor.
    // We use the ratio of resource's height to the height of design resolution,
    // this can make sure that the resource's height could fit for the height of design resolution.

    // if the frame's height is larger than the height of medium resource size, select large resource.
	if (frameSize.height > mediumResource.size.height)
	{
        searchPath.push_back(largeResource.directory);

        pDirector->setContentScaleFactor(MIN(largeResource.size.height/designResolutionSize.height, largeResource.size.width/designResolutionSize.width));
	}
    // if the frame's height is larger than the height of small resource size, select medium resource.
    else if (frameSize.height > smallResource.size.height)
    {
        searchPath.push_back(mediumResource.directory);
        
        pDirector->setContentScaleFactor(MIN(mediumResource.size.height/designResolutionSize.height, mediumResource.size.width/designResolutionSize.width));
    }
    // if the frame's height is smaller than the height of medium resource size, select small resource.
	else
    {
        searchPath.push_back(smallResource.directory);

        pDirector->setContentScaleFactor(MIN(smallResource.size.height/designResolutionSize.height, smallResource.size.width/designResolutionSize.width));
    }


    // set searching path
    CCFileUtils::sharedFileUtils()->setSearchPaths(searchPath);
	
    // 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);

    // create a scene. it's an autorelease object
    CCScene *pScene = HelloWorld::scene();

    // run
    pDirector->runWithScene(pScene);

    return true;
}