背景音乐功能

2 import android.content.Context;
3 import android.content.res.AssetFileDescriptor;
4 import android.media.MediaPlayer;
5 import android.util.Log;
6
7 /**
8  *
9  * This class is used for controlling background music
10  *
11  */
12 public class BackgroundMusic {
13
14     private static final String TAG = "Bg_Music";
15     private float mLeftVolume;
16     private float mRightVolume;
17     private Context mContext;
18     private MediaPlayer mBackgroundMediaPlayer;
19     private boolean mIsPaused;
20     private String mCurrentPath;
21
22     public BackgroundMusic(Context context){
23         this.mContext = context;
24         initData();
25     }
26     //初始化一些数据
27     private void initData(){
28             mLeftVolume =0.5f;
29             mRightVolume = 0.5f;
30             mBackgroundMediaPlayer = null;
31             mIsPaused = false;
32             mCurrentPath = null;
33     }
34
35     /**
36      * 根据path路径播放背景音乐
37      * @param path :assets中的音频路径
38      * @param isLoop  :是否循环播放
39      */
40     public void playBackgroundMusic(String path, boolean isLoop){
41         if (mCurrentPath == null){
42             //这是第一次播放背景音乐--- it is the first time to play background music
43             //或者是执行end()方法后，重新被叫---or end() was called
44             mBackgroundMediaPlayer = createMediaplayerFromAssets(path);
45             mCurrentPath = path;
46         }
47         else {
48             if (! mCurrentPath.equals(path)){
49                 //播放一个新的背景音乐--- play new background music
50                 //释放旧的资源并生成一个新的----release old resource and create a new one
51                 if (mBackgroundMediaPlayer != null){
52                     mBackgroundMediaPlayer.release();
53                 }
54                 mBackgroundMediaPlayer = createMediaplayerFromAssets(path);
55                 //记录这个路径---record the path
56                 mCurrentPath = path;
57               }
58         }
59
60         if (mBackgroundMediaPlayer == null){
61             Log.e(TAG, "playBackgroundMusic: background media player is null");
62         } else {
63             // 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
64             mBackgroundMediaPlayer.stop();
65             mBackgroundMediaPlayer.setLooping(isLoop);
66             try {
67                 mBackgroundMediaPlayer.prepare();
68                 mBackgroundMediaPlayer.seekTo(0);
69                 mBackgroundMediaPlayer.start();
70                 this.mIsPaused = false;
71             } catch (Exception e){
72                 Log.e(TAG, "playBackgroundMusic: error state");
73             }
74         }
75     }
76
77     /**
78      * 停止播放背景音乐
79      */
80     public void stopBackgroundMusic(){
81         if (mBackgroundMediaPlayer != null){
82             mBackgroundMediaPlayer.stop();
83             // should set the state, if not , the following sequence will be error
84             // play -> pause -> stop -> resume
85             this.mIsPaused = false;
86         }
87     }
88     /**
89      * 暂停播放背景音乐
90      */
91     public void pauseBackgroundMusic(){
92         if (mBackgroundMediaPlayer != null && mBackgroundMediaPlayer.isPlaying()){
93             mBackgroundMediaPlayer.pause();
94             this.mIsPaused = true;
95         }
96     }
97     /**
98      * 继续播放背景音乐
99      */
100     public void resumeBackgroundMusic(){
101         if (mBackgroundMediaPlayer != null && this.mIsPaused){
102             mBackgroundMediaPlayer.start();
103             this.mIsPaused = false;
104         }
105     }
106     /**
107      * 重新播放背景音乐
108      */
109     public void rewindBackgroundMusic(){
110         if (mBackgroundMediaPlayer != null){
111             mBackgroundMediaPlayer.stop();
112             try {
113                 mBackgroundMediaPlayer.prepare();
114                 mBackgroundMediaPlayer.seekTo(0);
115                 mBackgroundMediaPlayer.start();
116                 this.mIsPaused = false;
117             } catch (Exception e){
118                 Log.e(TAG, "rewindBackgroundMusic: error state");
119             }
120         }
121     }
122     /**
123      * 判断背景音乐是否正在播放
124      * @return：返回的boolean值代表是否正在播放
125      */
126     public boolean isBackgroundMusicPlaying(){
127         boolean ret = false;
128         if (mBackgroundMediaPlayer == null){
129             ret = false;
130         } else {
131             ret = mBackgroundMediaPlayer.isPlaying();
132         }
133         return ret;
134     }
135     /**
136      * 结束背景音乐，并释放资源
137      */
138     public void end(){
139         if (mBackgroundMediaPlayer != null){
140             mBackgroundMediaPlayer.release();
141         }
142         //重新“初始化数据”
143         initData();
144     }
145     /**
146      * 得到背景音乐的“音量”
147      * @return
148      */
149     public float getBackgroundVolume(){
150         if (this.mBackgroundMediaPlayer != null){
151             return (this.mLeftVolume + this.mRightVolume) / 2;
152         } else {
153             return 0.0f;
154         }
155     }
156     /**
157      * 设置背景音乐的音量
158      * @param volume：设置播放的音量，float类型
159      */
160     public void setBackgroundVolume(float volume){
161         this.mLeftVolume = this.mRightVolume = volume;
162         if (this.mBackgroundMediaPlayer != null){
163             this.mBackgroundMediaPlayer.setVolume(this.mLeftVolume, this.mRightVolume);
164         }
165     }
166     /**
167      * create mediaplayer for music
168      * @param path the path relative to assets
169      * @return
170      */
171     private MediaPlayer createMediaplayerFromAssets(String path){
172         MediaPlayer mediaPlayer = null;
173         try{
174             AssetFileDescriptor assetFileDescritor = mContext.getAssets().openFd(path);
175             mediaPlayer = new MediaPlayer();
176             mediaPlayer.setDataSource(assetFileDescritor.getFileDescriptor(),
177                     assetFileDescritor.getStartOffset(), assetFileDescritor.getLength());
178             mediaPlayer.prepare();
179             mediaPlayer.setVolume(mLeftVolume, mRightVolume);
180         }catch (Exception e) {
181             mediaPlayer = null;
182             Log.e(TAG, "error: " + e.getMessage(), e);
183         }
184         return mediaPlayer;
185     }
186 }
187
188