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cocos2dx 音频模块分析(4): 音效部分

我们上面几篇分析了cocos2dx音频模块的音乐部分，从这篇开始，我们分析下音效部分：1、//预加载音效文件：pszFilePath 音效文件名void SimpleAudioEngine::preloadEffect(const char* pszFilePath){    //获取音效文件的全路径，如果是apk包里的路径，则不包含assets/    std::string fullPath = getFullPathWithoutAssetsPrefix(pszFilePath);    preloadEffectJNI(fullPath.c_str());}--->>>// 这里通过jni调用java端的方法void preloadEffectJNI(const char *path)    {        // void preloadEffect(String)                JniMethodInfo methodInfo;                if (! getStaticMethodInfo(methodInfo, "preloadEffect", "(Ljava/lang/String;)V"))        {            return ;        }                jstring stringArg = methodInfo.env->NewStringUTF(path);        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID, stringArg);        methodInfo.env->DeleteLocalRef(stringArg);        methodInfo.env->DeleteLocalRef(methodInfo.classID);    }----->>>//Cocos2dxHelper类中的方法：public static void preloadEffect(final String path) {                //Cocos2dxSound类是专门处理音效的类		Cocos2dxHelper.sCocos2dSound.preloadEffect(path);	}--->>>//Cocos2dxSound类的方法：public int preloadEffect(final String pPath) {                //private final HashMap
   
     mPathSoundIDMap = new HashMap
    
     ();		//这个是音效路径对应音效ID的map		Integer soundID = this.mPathSoundIDMap.get(pPath);		if (soundID == null) {		        //			soundID = this.createSoundIDFromAsset(pPath);			// save value just in case if file is really loaded			// 如果createSoundIDFromAsset函数调用成功，则添加到mPathSoundIDMap中。			if (soundID != Cocos2dxSound.INVALID_SOUND_ID) {				this.mPathSoundIDMap.put(pPath, soundID);			}		}		return soundID;	}----->>>>根据我们传入的音效文件路径，加载音效	public int createSoundIDFromAsset(final String pPath) {		int soundID = Cocos2dxSound.INVALID_SOUND_ID;		try {		        //根据传入的路径不同，做不同处理，一个是绝对路径一个是包里的路径，加载音效文件			//The SoundPool class manages and plays audio resources for applications.			//private SoundPool mSoundPool;音效缓存池			if (pPath.startsWith("/")) {				soundID = this.mSoundPool.load(pPath, 0);			} else {				soundID = this.mSoundPool.load(this.mContext.getAssets().openFd(pPath), 0);			}		} catch (final Exception e) {			soundID = Cocos2dxSound.INVALID_SOUND_ID;			Log.e(Cocos2dxSound.TAG, "error: " + e.getMessage(), e);		}		// mSoundPool.load returns 0 if something goes wrong, for example a file does not exist		if (soundID == 0) {			soundID = Cocos2dxSound.INVALID_SOUND_ID;		}		return soundID;	}2、播放音效文件。pszFilePath：音效文件名；bLoop 是否循环播放unsigned int SimpleAudioEngine::playEffect(const char* pszFilePath, bool bLoop){    std::string fullPath = getFullPathWithoutAssetsPrefix(pszFilePath);    return playEffectJNI(fullPath.c_str(), bLoop);}----->>>playEffectJNI：   unsigned int playEffectJNI(const char* path, bool bLoop)    {        // int playEffect(String)                JniMethodInfo methodInfo;        int ret = 0;                if (! getStaticMethodInfo(methodInfo, "playEffect", "(Ljava/lang/String;Z)I"))        {            return ret;        }                jstring stringArg = methodInfo.env->NewStringUTF(path);        ret = methodInfo.env->CallStaticIntMethod(methodInfo.classID, methodInfo.methodID, stringArg, bLoop);        methodInfo.env->DeleteLocalRef(stringArg);        methodInfo.env->DeleteLocalRef(methodInfo.classID);                return (unsigned int)ret;    }------>>>>playEffect：public int playEffect(final String pPath, final boolean pLoop) {                //从mPathSoundIDMap中，根据音效path得到音效ID		Integer soundID = this.mPathSoundIDMap.get(pPath);		int streamID = Cocos2dxSound.INVALID_STREAM_ID;		if (soundID != null) {			// play sound			// 如果音效ID存在，则表明我们已经预先加载过这个音效文件，则调用mSoundPool.play直接播放			/*			private int doPlayEffect(final String pPath, final int soundId, final boolean pLoop) {				// play sound				// Play a sound from a sound ID.				// return non-zero streamID if successful, zero if failed如果成功会返回一个streamID				int streamID = this.mSoundPool.play(soundId, this.mLeftVolume, this.mRightVolume, Cocos2dxSound.SOUND_PRIORITY, pLoop ? -1 : 0, Cocos2dxSound.SOUND_RATE);				// record stream id				// 记录上面调用mSoundPool.play返回的streamID，至于为什么需要这样，看下面源码的说明：				// sound path and stream ids map				// a file may be played many times at the same time				// so there is an array map to a file path				// private final HashMap
     
      > mPathStreamIDsMap = new HashMap
      
       >();				ArrayList
       
         streamIDs = this.mPathStreamIDsMap.get(pPath);				if (streamIDs == null) {					streamIDs = new ArrayList
        
         (); this.mPathStreamIDsMap.put(pPath, streamIDs); } streamIDs.add(streamID); return streamID; } */ streamID = this.doPlayEffect(pPath, soundID.intValue(), pLoop); } else { // the effect is not prepared，如果音效没有预先加载，则需要先加载 soundID = this.preloadEffect(pPath); //加载音效文件 if (soundID == Cocos2dxSound.INVALID_SOUND_ID) { // can not preload effect return Cocos2dxSound.INVALID_SOUND_ID; } // only allow one playEffect at a time, or the semaphore will not work correctly synchronized(this.mSoundPool) { // add this effect into mEffecToPlayWhenLoadedArray, and it will be played when loaded completely // 这个应该和mSoundPool加载音效文件有关，我也不是很明白 /* 不过在初始化时设置了一个：this.mSoundPool.setOnLoadCompleteListener(new OnLoadCompletedListener()); //加载完成回调函数，应该和这个有关，这里我们就不关心了。 只需要知道如果我们提前加载音效文件 //也可以直接调用play函数，在调用play函数时会调用加载函数，并放入加载队列中，加载完成后进行播放。 //这样做会有一些延时，所以我们还是最好先加载，然后在播放。这个延时只在第一次播放时有，以后就不会了， //不过最好还是先加载。 */ /* @Override //加载完成回调函数。 public void onLoadComplete(SoundPool soundPool, int sampleId, int status) { if (status == 0) { // only play effect that are in mEffecToPlayWhenLoadedArray for ( SoundInfoForLoadedCompleted info : mEffecToPlayWhenLoadedArray) { if (sampleId == info.soundID) { // set the stream id which will be returned by playEffect() // 加载完成后调用doPlayEffect进行播放，并从mEffecToPlayWhenLoadedArray加载列表中 // 移除。 mStreamIdSyn = doPlayEffect(info.path, info.soundID, info.isLoop); // remove it from array, because we will break here // so it is safe to do mEffecToPlayWhenLoadedArray.remove(info); break; } } } else { mStreamIdSyn = Cocos2dxSound.INVALID_SOUND_ID; } mSemaphore.release(); } } */ mEffecToPlayWhenLoadedArray.add(new SoundInfoForLoadedCompleted(pPath, soundID.intValue(), pLoop)); try { // wait OnloadedCompleteListener to set streamID this.mSemaphore.acquire(); streamID = this.mStreamIdSyn; } catch(Exception e) { return Cocos2dxSound.INVALID_SOUND_ID; } } } return streamID; }
        
       
      
     
    
   

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