android实现背景音乐播放功能

package com.liu.zhen.utils;  import android.content.Context; import android.content.res.AssetFileDescriptor; import android.media.MediaPlayer; import android.util.Log;  /**  *  * This class is used for controlling background music  *  */ public class BackgroundMusic {   private static BackgroundMusic backgroundMusic = null;   private static final String TAG = "Bg_Music";   private float mLeftVolume;   private float mRightVolume;   private Context mContext;   private MediaPlayer mBackgroundMediaPlayer;   private boolean mIsPaused;   private String mCurrentPath;    private BackgroundMusic(Context context) {     this.mContext = context;     initData();   }    public static BackgroundMusic getInstance(Context context) {     if (backgroundMusic == null) {       backgroundMusic = new BackgroundMusic(context);     }     return backgroundMusic;   }    // 初始化一些数据   private void initData() {     mLeftVolume = 0.5f;     mRightVolume = 0.5f;     mBackgroundMediaPlayer = null;     mIsPaused = false;     mCurrentPath = null;   }    /**    * 根据path路径播放背景音乐    *    * @param path    *      :assets中的音频路径    * @param isLoop    *      :是否循环播放    */   public void playBackgroundMusic(String path, boolean isLoop) {     if (mCurrentPath == null) {       // 这是第一次播放背景音乐--- it is the first time to play background music       // 或者是执行end()方法后，重新被叫---or end() was called       mBackgroundMediaPlayer = createMediaplayerFromAssets(path);       mCurrentPath = path;     } else {       if (!mCurrentPath.equals(path)) {         // 播放一个新的背景音乐--- play new background music         // 释放旧的资源并生成一个新的----release old resource and create a new one         if (mBackgroundMediaPlayer != null) {           mBackgroundMediaPlayer.release();         }         mBackgroundMediaPlayer = createMediaplayerFromAssets(path);         // 记录这个路径---record the path         mCurrentPath = path;       }     }      if (mBackgroundMediaPlayer == null) {       Log.e(TAG, "playBackgroundMusic: background media player is null");     } else {       // 若果音乐正在播放或已近中断，停止它---if the music is playing or paused, stop it       mBackgroundMediaPlayer.stop();       mBackgroundMediaPlayer.setLooping(isLoop);       try {         mBackgroundMediaPlayer.prepare();         mBackgroundMediaPlayer.seekTo(0);         mBackgroundMediaPlayer.start();         this.mIsPaused = false;       } catch (Exception e) {         Log.e(TAG, "playBackgroundMusic: error state");       }     }   }    /**    * 停止播放背景音乐    */   public void stopBackgroundMusic() {     if (mBackgroundMediaPlayer != null) {       mBackgroundMediaPlayer.stop();       // should set the state, if not , the following sequence will be       // error       // play -> pause -> stop -> resume       this.mIsPaused = false;     }   }    /**    * 暂停播放背景音乐    */   public void pauseBackgroundMusic() {     if (mBackgroundMediaPlayer != null         && mBackgroundMediaPlayer.isPlaying()) {       mBackgroundMediaPlayer.pause();       this.mIsPaused = true;     }   }    /**    * 继续播放背景音乐    */   public void resumeBackgroundMusic() {     if (mBackgroundMediaPlayer != null && this.mIsPaused) {       mBackgroundMediaPlayer.start();       this.mIsPaused = false;     }   }    /**    * 重新播放背景音乐    */   public void rewindBackgroundMusic() {     if (mBackgroundMediaPlayer != null) {       mBackgroundMediaPlayer.stop();       try {         mBackgroundMediaPlayer.prepare();         mBackgroundMediaPlayer.seekTo(0);         mBackgroundMediaPlayer.start();         this.mIsPaused = false;       } catch (Exception e) {         Log.e(TAG, "rewindBackgroundMusic: error state");       }     }   }    /**    * 判断背景音乐是否正在播放    *    * @return：返回的boolean值代表是否正在播放    */   public boolean isBackgroundMusicPlaying() {     boolean ret = false;     if (mBackgroundMediaPlayer == null) {       ret = false;     } else {       ret = mBackgroundMediaPlayer.isPlaying();     }     return ret;   }    /**    * 结束背景音乐，并释放资源    */   public void end() {     if (mBackgroundMediaPlayer != null) {       mBackgroundMediaPlayer.release();     }     // 重新“初始化数据”     initData();   }    /**    * 得到背景音乐的“音量”    *    * @return    */   public float getBackgroundVolume() {     if (this.mBackgroundMediaPlayer != null) {       return (this.mLeftVolume + this.mRightVolume) / 2;     } else {       return 0.0f;     }   }    /**    * 设置背景音乐的音量    *    * @param volume    *      ：设置播放的音量，float类型    */   public void setBackgroundVolume(float volume) {     this.mLeftVolume = this.mRightVolume = volume;     if (this.mBackgroundMediaPlayer != null) {       this.mBackgroundMediaPlayer.setVolume(this.mLeftVolume,           this.mRightVolume);     }   }    /**    * create mediaplayer for music    *    * @param path    *      the path relative to assets    * @return    */   private MediaPlayer createMediaplayerFromAssets(String path) {     MediaPlayer mediaPlayer = null;     try {       AssetFileDescriptor assetFileDescritor = mContext.getAssets()           .openFd(path);       mediaPlayer = new MediaPlayer();       mediaPlayer.setDataSource(assetFileDescritor.getFileDescriptor(),           assetFileDescritor.getStartOffset(),           assetFileDescritor.getLength());       mediaPlayer.prepare();       mediaPlayer.setVolume(mLeftVolume, mRightVolume);     } catch (Exception e) {       mediaPlayer = null;       Log.e(TAG, "error: " + e.getMessage(), e);     }     return mediaPlayer;   } }