cocos2dx 音频模块分析(5): 音效部分

我们上一篇中分析的音效部分的预加载和播放函数，这一篇来分析下其他函数：
1、
暂停某个播放中的音效
//注意这里的nSoundId不是java端的soundID，而是streamID
//不要被参数的名字迷惑了。
void SimpleAudioEngine::pauseEffect(unsigned int nSoundId)
{
    pauseEffectJNI(nSoundId);
}
-->>
 void pauseEffectJNI(unsigned int nSoundId)
    {
        // void pauseEffect(int)

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "pauseEffect", "(I)V"))
        {
            return ;
        }

        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID, (int)nSoundId);
        methodInfo.env->DeleteLocalRef(methodInfo.classID);
    }
---->>//java端方法：
//pStreamID 这个参数，是调用unsigned int SimpleAudioEngine::playEffect()放回的StreamID
public void pauseEffect(final int pStreamID) {
	     /**
	     * Pause a playback stream. 暂停一个播放流
	     *
	     * Pause the stream specified by the streamID. This is the
	     * value returned by the play() function. (这个值是play函数的返回值)If the stream is
	     * playing, it will be paused. If the stream is not playing
	     * (e.g. is stopped or was previously paused), calling this
	     * function will have no effect.(如果处于播放状态则暂停，如果不处于播放状态，则无效)
	     *
	     * @param streamID a streamID returned by the play() function
	     */
		this.mSoundPool.pause(pStreamID);
	}
2、
 暂停所有音效
 void pauseAllEffectsJNI()
    {
        // void pauseAllEffects()

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "pauseAllEffects", "()V"))
        {
            return ;
        }

        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);
        methodInfo.env->DeleteLocalRef(methodInfo.classID);
    }
 --->>java端

 public void pauseAllEffects() {
	  /**
	     * Pause all active streams. //暂停所有正在播放的音效
	     *
	     * Pause all streams that are currently playing. This function
	     * iterates through all the active streams and pauses any that
	     * are playing. It also sets a flag so that any streams that
	     * are playing can be resumed by calling autoResume().
	     */
	      this.mSoundPool.autoPause();
	}

3、
 恢复播放某个音效
 void resumeEffectJNI(unsigned int nSoundId)
    {
        // void resumeEffect(int)

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "resumeEffect", "(I)V"))
        {
            return ;
        }

        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID, (int)nSoundId);
        methodInfo.env->DeleteLocalRef(methodInfo.classID);
    }
    --->>
    public void resumeEffect(final int pStreamID) {
	    /**
	     * Resume a playback stream.
	     * 只有处于暂停状态的stream，才可以恢复播放。
	     * Resume the stream specified by the streamID. This
	     * is the value returned by the play() function. If the stream
	     * is paused, this will resume playback. If the stream was not
	     * previously paused, calling this function will have no effect.
	     *
	     * @param streamID a streamID returned by the play() function
	     */
		this.mSoundPool.resume(pStreamID);
	}
4、
void resumeAllEffectsJNI()
    {
        // void resumeAllEffects()

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "resumeAllEffects", "()V"))
        {
            return ;
        }

        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);
        methodInfo.env->DeleteLocalRef(methodInfo.classID);
    }
---->>>java端函数：
	public void resumeAllEffects() {
		// can not only invoke SoundPool.autoResume() here, because
		// it only resumes all effects paused by pauseAllEffects()
		// 这里注释的很清楚
		if (!this.mPathStreamIDsMap.isEmpty()) {
			final Iterator<Entry<String, ArrayList<Integer>>> iter = this.mPathStreamIDsMap.entrySet().iterator();
			while (iter.hasNext()) {
				final Entry<String, ArrayList<Integer>> entry = iter.next();
				for (final int pStreamID : entry.getValue()) {
					this.mSoundPool.resume(pStreamID);
				}
			}
		}
	}
5、
停止播放某个音效，这里的nSoundId同样是pStreamID，停止播放的音效是不能
通过resume恢复播放的。
void SimpleAudioEngine::stopEffect(unsigned int nSoundId)
{
    stopEffectJNI(nSoundId);
}
--->>java端：
public void stopEffect(final int pStreamID) {
                  /**
		     * Stop a playback stream.
		     *
		     * Stop the stream specified by the streamID. This
		     * is the value returned by the play() function. If the stream
		     * is playing, it will be stopped. It also releases any native
		     * resources associated with this stream. (会释放对应的资源)If the stream is not
		     * playing, it will have no effect.
		     *
		     * @param streamID a streamID returned by the play() function
		     */
		this.mSoundPool.stop(pStreamID);

		// remove record
		// 从记录列表中移除
		for (final String pPath : this.mPathStreamIDsMap.keySet()) {
			if (this.mPathStreamIDsMap.get(pPath).contains(pStreamID)) {
				this.mPathStreamIDsMap.get(pPath).remove(this.mPathStreamIDsMap.get(pPath).indexOf(pStreamID));
				break;
			}
		}
	}
6、
void stopAllEffectsJNI()
    {
        // void stopAllEffects()

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "stopAllEffects", "()V"))
        {
            return ;
        }

        methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);
        methodInfo.env->DeleteLocalRef(methodInfo.classID);
    }
--->>>java端
	@SuppressWarnings("unchecked")
	public void stopAllEffects() {
		// stop effects，停止所有音效的播放
		if (!this.mPathStreamIDsMap.isEmpty()) {
			final Iterator<?> iter = this.mPathStreamIDsMap.entrySet().iterator();
			while (iter.hasNext()) {
				final Map.Entry<String, ArrayList<Integer>> entry = (Map.Entry<String, ArrayList<Integer>>) iter.next();
				for (final int pStreamID : entry.getValue()) {
					this.mSoundPool.stop(pStreamID);
				}
			}
		}

		// remove records，清空播放记录
		this.mPathStreamIDsMap.clear();
	}

7、
卸载加载的音效(重要)
//pszFilePath：音效文件名
void SimpleAudioEngine::unloadEffect(const char* pszFilePath)
{
    std::string fullPath = getFullPathWithoutAssetsPrefix(pszFilePath);
    unloadEffectJNI(fullPath.c_str());
}
--->>
 void unloadEffectJNI(const char* path)
    {
        // void unloadEffect(String)

        JniMethodInfo methodInfo;

        if (! getStaticMethodInfo(methodInfo, "unloadEffect", "(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);
    }
--->>>
public void unloadEffect(final String pPath) {
		// stop effects
		// 先停止
		final ArrayList<Integer> streamIDs = this.mPathStreamIDsMap.get(pPath);
		if (streamIDs != null) {
			for (final Integer pStreamID : streamIDs) {
				this.mSoundPool.stop(pStreamID);
			}
		}
		this.mPathStreamIDsMap.remove(pPath);

		// unload effect
		final Integer soundID = this.mPathSoundIDMap.get(pPath);
		if(soundID != null){

			    /**
			     * Unload a sound from a sound ID.
			     *
			     * Unloads the sound specified by the soundID. This is the value
			     * returned by the load() function. Returns true if the sound is
			     * successfully unloaded, false if the sound was already unloaded.
			     *
			     * @param soundID a soundID returned by the load() function
			     * @return true if just unloaded, false if previously unloaded
			     */
			// 卸载音效
			this.mSoundPool.unload(soundID);
			// 从mPathSoundIDMap中移除
			this.mPathSoundIDMap.remove(pPath);
		}
	}

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总结:
音效部分最重要的函数是preloadEffect，unloadEffect，playEffect，stopAllEffects
其他的感觉不是很常用，java有两个比较重要的map，一个是：
private final HashMap<String, Integer> mPathSoundIDMap = new HashMap<String, Integer>();
这个是用来存放所有加载的音效文件路径和SoundID的map。
一个是：
	// sound path and stream ids map cocos2dx原本注释
	// a file may be played many times at the same time
	// so there is an array map to a file path
private final HashMap<String, ArrayList<Integer>> mPathStreamIDsMap = new HashMap<String, ArrayList<Integer>>();
用来存放所有播放的音效文件路径和StreamIDs的map。
注意：这里的SoundID和StreamID不是一个概念，一个音效文件只对应一个SoundID，而却可以对应多个StreamID，因为一个
音效文件可以播放多次(StreamID)，但是只需要加载一次(SoundID).

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