Cocos2dx Android工程的啓動過程

一、安卓工程下的設置啓動activity爲src下面的AppActivity,啓動調用的onCreate並無作過多的事情，只是調用了父類Cocos2dxActivity的onCreate。AppActivity代碼以下：

import org.cocos2dx.lib.Cocos2dxActivity;

public class AppActivity extends Cocos2dxActivity {
    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ......
    }
}

二、Cocos2dxActivity在cocos/platform/android/java/src/org/cocos2dx/lib/Cocos2dxActivity.java裏，查看onCreate,代碼以下：

@Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initFMOD(); //加載聲音庫
        try {
            Class.forName("android.os.AsyncTask");
        } catch (Throwable ignor) {
            ignor.printStackTrace();
        }
        sContext = this;
        PSNetwork.init(sContext); //初始化安卓網絡鏈接服務
        if (Build.VERSION.SDK_INT >= 23) {
            requestUserPermissions(); //系統的部分受權
        }
        mMacAddress = MacAddressUtil.getMacAddress(sContext);//獲取wifi的MAC地址
        CocosPlayClient.init(this, false); //暫時無用
        boolean isLoadOK = onLoadNativeLibraries(); //把工程中libs下面的so文件load進來，定義在AndroidManifest, meta-data標籤下，android.app.lib_name. 最終在包的data/data/com.XXX.XXX/lib下面
        if (false == isLoadOK) {
            return;
        }

        this.mHandler = new Cocos2dxHandler(this);//處理安卓的彈窗等

        Cocos2dxHelper.init(this);

        this.mGLContextAttrs = getGLContextAttrs();//獲取OpenGLEs的相關屬性
        this.init(); //說明以下文

        if (mVideoHelper == null) {
            mVideoHelper = new Cocos2dxVideoHelper(this, mFrameLayout);
        }

        if (mWebViewHelper == null) {
            mWebViewHelper = new Cocos2dxWebViewHelper(mFrameLayout);
        }

        if(mEditBoxHelper == null){
            mEditBoxHelper = new Cocos2dxEditBoxHelper(mFrameLayout);
        }
        if (null == mScreenListener) {
            mScreenListener = new ScreenListener(this);
            mScreenListener.begin(this);
        }
    }

三、Cocos2dxActivity的init函數以下：

public void init() {
        // FrameLayout
        ViewGroup.LayoutParams framelayout_params = new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        mFrameLayout = new ResizeLayout(this); //繼承自FrameLayout,當作是一塊畫布(canvas),其餘控件添加在上面
        mFrameLayout.setLayoutParams(framelayout_params);

        // Cocos2dxEditText layout
        ViewGroup.LayoutParams edittext_layout_params = new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.WRAP_CONTENT);
        Cocos2dxEditBox edittext = new Cocos2dxEditBox(this);
        edittext.setLayoutParams(edittext_layout_params);//輸入框

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

        // Cocos2dxGLSurfaceView
        this.mGLSurfaceView = this.onCreateView();//建立遊戲的渲染，接受輸入事件的OpenGL類

        // ...add to FrameLayout
        mFrameLayout.addView(this.mGLSurfaceView);//添加到畫布上

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

        this.mGLSurfaceView.setCocos2dxRenderer(new Cocos2dxRenderer());//註冊自主實現的渲染器,內容以下
        this.mGLSurfaceView.setCocos2dxEditText(edittext);//輸入框

        this.onCreateFrameLayout();
        // Set framelayout as the content view
        setContentView(mFrameLayout);//設置這個Activity的顯示界面
    }

四、Cocos2dxRenderer,cocos2dx的渲染器，繼承自android.opengl.GLSurfaceView.Renderer，當3中的GLSurfaceView被建立的時候會調用render的onSurfaceCreated()方法; 當GLSurfaceView大小或者橫豎屏發生變化的時候調用render的onSurfaceChanged()方法； 當系統每一次從新畫GLSurfaceView的時候，調用onDrawFrame()方法。因此Cocos2dxRender對這三個方法進行了重寫。

@Override
    public void onSurfaceCreated(final GL10 GL10, final EGLConfig EGLConfig) {
        Cocos2dxRenderer.nativeInit(this.mScreenWidth, this.mScreenHeight);//此處調用了一個定義爲native的函數，設置glview等，經過jni來訪問c++實現的方法，接口實如今cocos/platform/android/javaactivity-android.cpp裏面，下面的5會繼續講
        this.mLastTickInNanoSeconds = System.nanoTime();
        mNativeInitCompleted = true;
        try{
            Cocos2dxActivity activity = (Cocos2dxActivity) Cocos2dxActivity.getContext();
            activity.onSurfaceCreated(this, GL10, EGLConfig);
        }catch( Throwable e ){
            e.printStackTrace();
        }
    }

@Override
    public void onDrawFrame(final GL10 gl) { //系統自動每秒鐘調用60次這個函數
        /*
         * No need to use algorithm in default(60 FPS) situation, since
         * onDrawFrame() was called by system 60 times per second by default.
         */
        if( true == mIsPaused ){
            return;
        }
        if( mDelayResumeCount <= DELAY_RESUME_COUNT ){
            mDelayResumeCount = mDelayResumeCount + 1;
            if( mDelayResumeCount == DELAY_RESUME_COUNT ){
                Cocos2dxRenderer.nativeOnResume();
                try{
                    Cocos2dxActivity activity = (Cocos2dxActivity) Cocos2dxActivity.getContext();
                    activity.nativeResume();
                }catch( Throwable e ){
                    e.printStackTrace();
                }
            }
            return;
        }
        if (sAnimationInterval <= 1.0 / 60 * Cocos2dxRenderer.NANOSECONDSPERSECOND) {
            Cocos2dxRenderer.nativeRender(); //大於等於每秒60幀則不通過算法處理，直接執行nativeRender，將在6中有說明
        } else {
            final long now = System.nanoTime();
            final long interval = now - this.mLastTickInNanoSeconds;

            if (interval < Cocos2dxRenderer.sAnimationInterval) { //按照設置的幀數，若是沒有到時間，則sleep到相應的時間
                try {
                    Thread.sleep((Cocos2dxRenderer.sAnimationInterval - interval)
                            / Cocos2dxRenderer.NANOSECONDSPERMICROSECOND);
                } catch (final Exception e) {
                }
            }
            /*
             * Render time MUST be counted in, or the FPS will slower than
             * appointed.
             */
            this.mLastTickInNanoSeconds = System.nanoTime();
            Cocos2dxRenderer.nativeRender();
        }
        try{
            Cocos2dxActivity activity = (Cocos2dxActivity) Cocos2dxActivity.getContext();
            activity.onDrawFrame(this, gl);
        }catch( Throwable e ){
            e.printStackTrace();
        }
    }

@Override
    public void onSurfaceChanged(final GL10 GL10, final int width,
            final int height) {
        Cocos2dxRenderer.nativeOnSurfaceChanged(width, height);
        try{
            Cocos2dxActivity activity = (Cocos2dxActivity) Cocos2dxActivity.getContext();
            activity.onSurfaceChanged(this, GL10, width, height);
        }catch( Throwable e ){
            e.printStackTrace();
        }
    }

五、 4裏面onSurfaceCreated的nativeInit的實現放在cocos/platform/android/javaactivity-android.cpp，方法以下：

void Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeInit(JNIEnv*  env, jobject thiz, jint w, jint h)
{
    auto director = cocos2d::Director::getInstance();
    auto glview = director->getOpenGLView();
    if (!glview)
    {
        glview = cocos2d::GLViewImpl::create("Android app");
        glview->setFrameSize(w, h);
        director->setOpenGLView(glview); //設置glview

        //cocos_android_app_init(env, thiz);

        cocos2d::Application::getInstance()->run(); //程序開始運行，android的Application實現放在CCApplication-android.cpp,run的代碼以下
    }
    else
    {
        cocos2d::GL::invalidateStateCache();
        cocos2d::GLProgramCache::getInstance()->reloadDefaultGLPrograms();
        cocos2d::DrawPrimitives::init();
        cocos2d::VolatileTextureMgr::reloadAllTextures();

        cocos2d::EventCustom recreatedEvent(EVENT_RENDERER_RECREATED);
        director->getEventDispatcher()->dispatchEvent(&recreatedEvent);
        director->setGLDefaultValues();
    }
}

int Application::run()
{
    // Initialize instance and cocos2d.
    if (! applicationDidFinishLaunching()) //applicationDidFinishLanunching在本身的Classes/AppDelegate進行重寫,遊戲已經啓動
    {
        return 0;
    }
    
    return -1;
}

bool AppDelegate::applicationDidDinishLaunching()
{
    ......
    director->setOpenGLView(glview);
    director->setAnimationInterval(1/30.f); //設置幀數，會調用Application-android的setAnimationInterval,再經過JniHelper調用Cocos2dxRenderer中的setAnimationInterval
    director->runWithScene(scene); //
    return true
}

六、關於4中onDrawFrame涉及到的函數nativeRender，它也是一個native類型的函數，實現放在cocos/platform/android/jni/Java_org_cocos2dx_lib_Cocos2dxRenderer.cpp

JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeRender(JNIEnv* env) {
        cocos2d::Director::getInstance()->mainLoop(); //進入遊戲的主循環，Director的mainLoop，事件的分發，渲染,內存池的管理
    }