Android cocos2dx遊戲開發——示例程序HelloCpp源碼分析

  本文通過分析cocos2dx提供的示例程序HelloCpp來分析cocos2dx的啓動過程。

      我們從HelloCpp.java開始：

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");
    }
}

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是一個Activity，首先會執行靜態代碼塊，加載libhellocpp.so庫，然後就是執行onCreate方法，這裏調用了父類的onCreate方法。我們看看Cocos2dxActivity的onCreate方法，該類在cocos2dx的庫工程libcocos2dx中：

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

        this.init();

        Cocos2dxHelper.init(this, this);
    }

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

    	this.init();

		Cocos2dxHelper.init(this, this);
	}

      這裏主要是執行初始化過程，Cocos2dxHandler主要處理顯示Dialog的消息，Cocos2dxHelper是個輔助類，我們主要看init()方法：

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);
    }

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);
	}

      這裏就是爲Activity綁定View Hierarchy，大家做Android開發的對着一定很熟悉。View Hierarchy的根View是個FrameLayout，FrameLayout又包含一個EditText和一個GLSurfaceView，這個GLSurfaceView就是cocos引擎用來繪製遊戲畫面的關鍵View，我們來詳細分析一下它。首先看一下Cocos2dxActivity的onCreateView方法：

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

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

      該方法就是新建一個Cocos2dxGLSurfaceView，Cocos2dxGLSurfaceView又繼承於GLSurfaceView。我們都知道GLSurfaceView的核心就是Renderer，初始化時會調用Renderer的onSurfaceCreated方法，每一幀的繪製是通過調用Renderer的onDrawFrame方法。Cocos2dxGLSurfaceView的Renderer是一個Cocos2dxRenderer對象，我們先來看Cocos2dxRenderer對象的onSurfaceCreated方法：

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

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

      這裏調用了一個本地方法nativeInit(final int pWidth, final int pHeight)，本地方法的實現在jni/hellocpp/main.cpp中實現的：

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
    {
        ......
    }
}

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是遊戲的導演類，一個遊戲只有一個導演類用來控制和管理場景。CCDirector::sharedDirector()是個靜態方法，用來獲取導演類的單例對象：

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

    return s_SharedDirector;
}

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

    return s_SharedDirector;
}

      CCCCDisplayLinkDirector是CCDirector的子類。我們再回到nativeinit方法中，獲取到導演類的單例對象後又調用了它的getOpenGLView()方法：

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

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

      該方法返回用於遊戲繪製的CCEGLView，在Android平臺下，這個CCEGLView其實沒有什麼作用，因爲遊戲都是繪製在Cocos2dxGLSurfaceView上的。由於我們是初始化過程，所以此時m_pobOpenGLView爲null，所以if (!CCDirector::sharedDirector()->getOpenGLView())條件成立，執行以下的代碼：

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

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

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

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

     同樣，我們先獲取一個CCEGLView的單例對象，接下來又新建了一個AppDelegate對象，大家可能在工程中找不到AppDelegate類。我們打開工程目錄的上一級目錄：
      我們的Android工程是在proj.android文件夾中，而AppDelegate類就在Classes文件夾中。因爲cocos2dx是跨平臺的，而AppDelegate在各個平臺之間是通用的不需要修改的，所以就放在一個公用的目錄下。

#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_

#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是繼承CCApplication類的，我們看一下CCApplication的構造方法：

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

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

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

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

      我們看到在新建CCApplication對象時，會把該對象賦給一個全局變量sm_pSharedApplication。所以我們在new AppDelegate()的時候，就把它象賦給全局變量sm_pSharedApplication。我們再看下CCApplication的CCApplication::sharedApplication方法：

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

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

      此時，sm_pSharedApplication指向的是一個AppDelegate對象。所以我們執行CCApplication::sharedApplication()->run()時其實執行的是AppDelegate對象的run方法。現在我們應該明白這個類爲什麼叫AppDelegate了，因爲CCApplication的工作實際都委託給了AppDelegate類了。看一下AppDelegate的方法：

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

    return -1;
}

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

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;
}

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;
}