Cocos2dx audio module Analysis (2): background music, cocos2dx Module

Cocos2dx audio module Analysis (2): background music, cocos2dx Module

Cocos2dx audio module Analysis (2): Background Music Section

I have analyzed some things in (1). Next I will analyze the background music file playback Based on the android platform: 1. This is only the pre-loading of background music. Why is pre-loading required? It is time-consuming to load music files. If we do not pre-load the file, we can play it directly, but there will be a certain delay, because if there is no pre-load, we can play it directly, it will first load the music file and then play it. Void SimpleAudioEngine: preloadBackgroundMusic (const char * pszFilePath) {std: string fullPath = getFullPathWithoutAssetsPrefix (pszFilePath); preloadBackgroundMusicJNI (fullPath. c_str ();} loads background music and calls the android end: public void preloadBackgroundMusic (final String pPath) {if (this. mCurrentPath = null) | (! This. mCurrentPath. equals (pPath) {// preload new background music // release old resource and create a new one // if we play a new background music file, then we need to release the old player and then create a new // Releases resources associated with this MediaPlayer object. if (this. mBackgroundMediaPlayer! = Null) {this. mBackgroundMediaPlayer. release ();} // create a media player instance called the MediaPlayer class this. mBackgroundMediaPlayer = this. createMediaplayer (pPath); // record the path // record the currently played background music file, because the next time you play the same music // file, then we can play the video directly without re-creating the MediaPlayer instance this. mCurrentPath = pPath ;}----- >>>/*** create mediaplayer for music ** @ param pPath * the pPath relative to assets * @ return */private MediaPlayer createMediaplayer (fina L String pPath) {MediaPlayer mediaPlayer = new MediaPlayer (); try {// differentiate the absolute path from the path in the package. When the final goal is to set the playback source if (pPath. startsWith ("/") {final FileInputStream FD = new FileInputStream (pPath); mediaPlayer. setDataSource (FCM. getFD (); FCM. close ();} else {final AssetFileDescriptor assetFileDescritor = this. mContext. getAssets (). openFd (pPath); mediaPlayer. setDataSource (assetFileDescritor. getFileDescriptor (), asset FileDescritor. getStartOffset (), assetFileDescritor. getLength ();} // prepare for the player. This is only an android api. If you do not understand it, check the document. /*** Prepares the player for playback, synchronously. ** After setting the datasource and the display surface, you need to either * call prepare () or prepareAsync (). for files, it is OK to call prepare (), * which blocks until MediaPlayer is ready for playback. ** @ throws IllegalStateException if it is called in an invalid state */mediaPlayer. prepare (); // sets the sound volume mediaPlayer. setVolume (this. mLeftVol Ume, this. mRightVolume);} catch (final Exception e) {mediaPlayer = null; Log. e (Cocos2dxMusic. TAG, "error:" + e. getMessage (), e) ;}return mediaPlayer;} 2. music playing function // pszFilePath: music file name // bLoop: whether to play the video cyclically. We usually set the music file to play cyclically, void SimpleAudioEngine: playBackgroundMusic (const char * pszFilePath, bool bLoop) {std: string fullPath = callback (pszFilePath); playBackgroundMusicJNI (fullPath. c_st R (), bLoop) ;}--- >>> in the end, the playBackgroundMusic function on the android end is called, and the file path and whether to cyclically play in public void playBackgroundMusic (final String path, final boolean isLoop) {if (mCurrentPath = null) {// it is the first time to play background music or end () was called // if no music file has been played before, re-create one. The above English note clearly shows mBackgroundMediaPlayer = createMediaplayer (path); mCurrentPath = path;} else {if (! MCurrentPath. equals (path) {// play new background music // if the music file played this time is different from the previous one, it is a new music file, // release the old one and create a new one. // Release old resource and create a new oneif (mBackgroundMediaPlayer! = Null) {mBackgroundMediaPlayer. release ();} mBackgroundMediaPlayer = createMediaplayer (path); // record the pathmCurrentPath = path ;}} if (mBackgroundMediaPlayer = null) {Log. e (Cocos2dxMusic. TAG, "playBackgroundMusic: background media player is null");} else {try {// if the music is playing or paused, stop it // For playing or paused, if (mPaused) {// if it is paused, set the playback progress to 0 and start. // This means that if we call pause and then call play, the // music will be played from the beginning, rather than from the paused place. /*** Seeks to specified time position. ** @ param msec the offset in milliseconds from the start to seek to * @ throws IllegalStateException if the internal player engine has not been * initialized */mBackgroundMediaPlayer. seekTo (0);/*** Starts (start) or resumes playback (resume ). if playback had previusly been paused, * playback will continue from where it was paused. if playback had * been stopped, Or never started before, playback will start at the * beginning. * The start function has two functions: one is to start playing and the other is to resume playing. * 1. If stopped or never started before (the first time ), start playing from scratch. * 2. If paused is paused, it will be played from where it is paused. */MBackgroundMediaPlayer. start ();} else if (mBackgroundMediaPlayer. isPlaying () {// if it is in the playing status, it will return to the start and play mBackgroundMediaPlayer from the beginning. seekTo (0);} else {// if it is in the stop State, it will be played again. The preceding two functions of the start function are described in mBackgroundMediaPlayer. start () ;}/ * conclusion: in fact, the above three cases are handled separately, and the final effect is the same, that is, playing the background music file from the beginning. * /// Set whether to play mBackgroundMediaPlayer cyclically. setLooping (isLoop); // mPaused indicates that the value is set to false; mPaused = false; // whether the loop playback record is mIsLoop = isLoop;} catch (final Exception e) {Log. e (Cocos2dxMusic. TAG, "playBackgroundMusic: error state") ;}}3. Conclusion: From the analysis above, we can know that if you load the file in advance, you can create a MediaPlayer first, we can play the video directly during playback. If we do not pre-load the video in advance, we can call the playBackgroundMusic function directly or play the video, but there will be a MediaPlayer creation process, there will be some time delay.