cocos2dx 音频模块分析(3):背景音乐部分
我在(2)已经分析了背景音乐文件的预加载preloadBackgroundMusic和播放playBackgroundMusic两个函数，这里接着分析，还是基于android平台：1、//暂停函数，用于音乐的暂停void SimpleAudioEngine::pauseBackgroundMusic(){//在SimpleAudioEngineJni.cpp源文件中定义pauseBackgroundMusicJNI();}//–pauseBackgroundMusicJNI—>>>void pauseBackgroundMusicJNI(){// void pauseBackgroundMusic()JniMethodInfo methodInfo;if (! getStaticMethodInfo(methodInfo, "pauseBackgroundMusic", "()V")){return;}//通过jni调用java端的函数，调用的是Cocos2dxHelper类中的/*public static void pauseBackgroundMusic() {Cocos2dxHelper.sCocos2dMusic.pauseBackgroundMusic();}*/methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);}最终调用的是Cocos2dxMusic类中的public void pauseBackgroundMusic() {//mBackgroundMediaPlayer在(2)中有分析过，创建的MediaPlayer实例if (this.mBackgroundMediaPlayer != null && this.mBackgroundMediaPlayer.isPlaying()) {this.mBackgroundMediaPlayer.pause();this.mPaused = true; //是否暂停标志}}2、恢复播放void SimpleAudioEngine::resumeBackgroundMusic(){resumeBackgroundMusicJNI();}其实和上面暂停的调用过程是一样的，就不分析了，直接进入java端看最终调用的函数,public void resumeBackgroundMusic() {//这里只有处于暂停状态时即mPaused变量为true时，，才会接着//上次播放的位置开始播放if (this.mBackgroundMediaPlayer != null && this.mPaused) {this.mBackgroundMediaPlayer.start();this.mPaused = false; //把暂停标志位设置false}}3、从头开始播放音乐文件void rewindBackgroundMusicJNI(){// void rewindBackgroundMusic()JniMethodInfo methodInfo;if (! getStaticMethodInfo(methodInfo, "rewindBackgroundMusic", "()V")){return;}methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);}—>>//java端函数//这个函数最终也是会调用playBackgroundMusic函数，但是和playBackgroundMusic有一点不同，//playBackgroundMusic需要传入音乐文件名，可以播放和上一次一样的音乐也可以和是上一次不一样的//音乐，但是rewindBackgroundMusic函数只有在mBackgroundMediaPlayer不为null时才执行，//也就是必须播放过音乐，且播放的是上次播放的音乐，只不过这次是从头开始播放public void rewindBackgroundMusic() {if (this.mBackgroundMediaPlayer != null) {playBackgroundMusic(mCurrentPath, mIsLoop);}}4、停止播放音乐文件void stopBackgroundMusicJNI(){// void stopBackgroundMusic()JniMethodInfo methodInfo;if (! getStaticMethodInfo(methodInfo, "stopBackgroundMusic", "()V")){return;}methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);}—>>>//java端函数：public void stopBackgroundMusic() {if (this.mBackgroundMediaPlayer != null) {mBackgroundMediaPlayer.release();//不太明白这里为什么有从新创建了MediaPlayer实例//可能是一些特殊情况下会出现问题？mBackgroundMediaPlayer = createMediaplayer(mCurrentPath);// should set the state, if not, the following sequence will be error// play -> pause -> stop -> resume//为什么设置mPaused标志，直接看上面的英文注释this.mPaused = false;}}5、返回是否处于播放状态 bool isBackgroundMusicPlayingJNI(){// boolean rewindBackgroundMusic()JniMethodInfo methodInfo;jboolean ret = false;if (! getStaticMethodInfo(methodInfo, "isBackgroundMusicPlaying", "()Z")){return ret;}ret = methodInfo.env->CallStaticBooleanMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);return ret;}—>>>//java端函数，没什么东西public boolean isBackgroundMusicPlaying() {boolean ret = false;if (this.mBackgroundMediaPlayer == null) {ret = false;} else {ret = this.mBackgroundMediaPlayer.isPlaying();}return ret;}6、获取播放声音音量值float getBackgroundMusicVolumeJNI(){// float getBackgroundMusicVolume()JniMethodInfo methodInfo;jfloat ret = -1.0;if (! getStaticMethodInfo(methodInfo, "getBackgroundMusicVolume", "()F")){return ret;}ret = methodInfo.env->CallStaticFloatMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);return ret;}——->>>//javapublic float getBackgroundVolume() {if (this.mBackgroundMediaPlayer != null) {return (this.mLeftVolume + this.mRightVolume) / 2;} else {return 0.0f;}} 7、设置声音音量值void setBackgroundMusicVolumeJNI(float volume){// void setBackgroundMusicVolume()JniMethodInfo methodInfo;if (! getStaticMethodInfo(methodInfo, "setBackgroundMusicVolume", "(F)V")){return ;}methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID, volume);methodInfo.env->DeleteLocalRef(methodInfo.classID);} —->>>java public void setBackgroundVolume(float pVolume) {if (pVolume < 0.0f) {pVolume = 0.0f;}if (pVolume > 1.0f) {pVolume = 1.0f;}this.mLeftVolume = this.mRightVolume = pVolume;if (this.mBackgroundMediaPlayer != null) {this.mBackgroundMediaPlayer.setVolume(this.mLeftVolume, this.mRightVolume);}}8、end函数，这个一般在退出游戏是调用，关掉所有的音乐和音效。 void endJNI(){// void end()JniMethodInfo methodInfo;if (! getStaticMethodInfo(methodInfo, "end", "()V")){return ;}methodInfo.env->CallStaticVoidMethod(methodInfo.classID, methodInfo.methodID);methodInfo.env->DeleteLocalRef(methodInfo.classID);}—>>>//java端函数public static void end() {Cocos2dxHelper.sCocos2dMusic.end(); //背景音乐文件的处理Cocos2dxHelper.sCocos2dSound.end();}—->>>>/////背景音乐文件的处理public void end() {if (this.mBackgroundMediaPlayer != null) {this.mBackgroundMediaPlayer.release();}//把所有的变量恢复初始值/*private void initData() {this.mLeftVolume = 0.5f;this.mRightVolume = 0.5f;this.mBackgroundMediaPlayer = null;this.mPaused = false;this.mCurrentPath = null;}*/this.initData();}
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