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; 
} 
}