Android提高21篇之二十：MediaPlayer播放網絡音頻

       以前曾經地介紹過MediaPlayer的基本用法，這裡就深入地講解MediaPlayer的在線播放功能。本文主要實現MediaPlayer在線播放音頻的功能，由於在線視頻播放比在線音頻播放復雜，因此先介紹在線音頻播放的實現，這樣可以幫助大家逐步深入了解MediaPlayer的在線播放功能。先來看看本文程序運行的結果：

      main.xml的源碼如下：

1. <framelayout xmlns:android="http://schemas.android.com/apk/res/android"   
2.         android:layout_height="fill_parent" android:layout_width="fill_parent">  
3.         <linearlayout android:layout_height="wrap_content"   
4.                 android:layout_width="fill_parent" android:orientation="vertical"  
5.                 android:layout_gravity="top">  
6.                 <linearlayout android:orientation="horizontal"   
7.                         android:layout_gravity="center_horizontal" android:layout_marginTop="4.0dip"  
8.                         android:layout_height="wrap_content" android:layout_width="wrap_content">  
9.                         <button android:layout_width="wrap_content"   
10.                                 android:layout_height="wrap_content" android:id="@+id/btnPlayUrl"  
11.                                 android:text="播放網絡音頻">  
12.                         <button android:layout_height="wrap_content" android:id="@+id/btnPause"   
13.                                 android:text="暫停" android:layout_width="80dip">  
14.                         <button android:layout_height="wrap_content"   
15.                                 android:layout_width="80dip" android:text="停止" android:id="@+id/btnStop">  
16.                   
17.                 <linearlayout android:orientation="horizontal"   
18.                         android:layout_width="fill_parent" android:layout_height="wrap_content"  
19.                         android:layout_marginBottom="20dip">  
20.                         <seekbar android:paddingright="10dip" android:layout_gravity="center_vertical"   
21.                                 android:paddingLeft="10dip" android:layout_weight="1.0"  
22.                                 android:layout_height="wrap_content" android:layout_width="wrap_content"  
23.                                 android:id="@+id/skbProgress" android:max="100">  

       Player.java是本文的核心，Player.java實現了“進度條更新”、“數據緩沖”等功能，雖然不是很復雜的功能，但卻是非常有用的功能。Player.java源碼如下：

1. package com.musicplayer;  
2.   
3.   
4. import java.io.IOException;  
5. import java.util.Timer;  
6. import java.util.TimerTask;  
7. import android.media.AudioManager;  
8. import android.media.MediaPlayer;  
9. import android.media.MediaPlayer.OnBufferingUpdateListener;  
10. import android.media.MediaPlayer.OnCompletionListener;  
11. import android.os.Handler;  
12. import android.os.Message;  
13. import android.util.Log;  
14. import android.widget.SeekBar;  
15.   
16. public class Player implements OnBufferingUpdateListener,  
17.                 OnCompletionListener, MediaPlayer.OnPreparedListener{  
18.         public MediaPlayer mediaPlayer;  
19.         private SeekBar skbProgress;  
20.         private Timer mTimer=new Timer();  
21.         public Player(SeekBar skbProgress)  
22.         {  
23.                 this.skbProgress=skbProgress;  
24.                   
25.                 try {  
26.                         mediaPlayer = new MediaPlayer();  
27.                         mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);  
28.                         mediaPlayer.setOnBufferingUpdateListener(this);  
29.                         mediaPlayer.setOnPreparedListener(this);  
30.                 } catch (Exception e) {  
31.                         Log.e("mediaPlayer", "error", e);  
32.                 }  
33.                   
34.                 mTimer.schedule(mTimerTask, 0, 1000);  
35.         }  
36.           
37.         /******************************************************* 
38.          * 通過定時器和Handler來更新進度條 
39.          ******************************************************/  
40.         TimerTask mTimerTask = new TimerTask() {  
41.                 @Override  
42.                 public void run() {  
43.                         if(mediaPlayer==null)  
44.                                 return;  
45.                         if (mediaPlayer.isPlaying() && skbProgress.isPressed() == false) {  
46.                                 handleProgress.sendEmptyMessage(0);  
47.                         }  
48.                 }  
49.         };  
50.           
51.         Handler handleProgress = new Handler() {  
52.                 public void handleMessage(Message msg) {  
53.   
54.                         int position = mediaPlayer.getCurrentPosition();  
55.                         int duration = mediaPlayer.getDuration();  
56.                           
57.                         if (duration > 0) {  
58.                                 long pos = skbProgress.getMax() * position / duration;  
59.                                 skbProgress.setProgress((int) pos);  
60.                         }  
61.                 };  
62.         };  
63.         //*****************************************************  
64.           
65.         public void play()  
66.         {  
67.                 mediaPlayer.start();  
68.         }  
69.           
70.         public void playUrl(String videoUrl)  
71.         {  
72.                 try {  
73.                         mediaPlayer.reset();  
74.                         mediaPlayer.setDataSource(videoUrl);  
75.                         mediaPlayer.prepare();//prepare之後自動播放  
76.                         //mediaPlayer.start();  
77.                 } catch (IllegalArgumentException e) {  
78.                         // TODO Auto-generated catch block  
79.                         e.printStackTrace();  
80.                 } catch (IllegalStateException e) {  
81.                         // TODO Auto-generated catch block  
82.                         e.printStackTrace();  
83.                 } catch (IOException e) {  
84.                         // TODO Auto-generated catch block  
85.                         e.printStackTrace();  
86.                 }  
87.         }  
88.   
89.           
90.         public void pause()  
91.         {  
92.                 mediaPlayer.pause();  
93.         }  
94.           
95.         public void stop()  
96.         {  
97.                 if (mediaPlayer != null) {   
98.                         mediaPlayer.stop();  
99.             mediaPlayer.release();   
100.             mediaPlayer = null;   
101.         }   
102.         }  
103.   
104.         @Override  
105.         /**  
106.          * 通過onPrepared播放  
107.          */  
108.         public void onPrepared(MediaPlayer arg0) {  
109.                 arg0.start();  
110.                 Log.e("mediaPlayer", "onPrepared");  
111.         }  
112.   
113.         @Override  
114.         public void onCompletion(MediaPlayer arg0) {  
115.                 Log.e("mediaPlayer", "onCompletion");  
116.         }  
117.   
118.         @Override  
119.         public void onBufferingUpdate(MediaPlayer arg0, int bufferingProgress) {  
120.                 skbProgress.setSecondaryProgress(bufferingProgress);  
121.                 int currentProgress=skbProgress.getMax()*mediaPlayer.getCurrentPosition()/mediaPlayer.getDuration();  
122.                 Log.e(currentProgress+"% play", bufferingProgress + "% buffer");  
123.         }  
124.   
125. }  

       test_musicplayer.java是主程序，負責調用Player類，其中關鍵部分是SeekBarChangeEvent這個SeekBar拖動的事件：SeekBar的Progress是0~SeekBar.getMax()之內的數，而MediaPlayer.seekTo()的參數是0~MediaPlayer.getDuration()之內數，所以MediaPlayer.seekTo()的參數是(progress/seekBar.getMax())*player.mediaPlayer.getDuration()。test_musicplayer.java源碼如下：

1. package com.musicplayer;  
2.   
3. import android.app.Activity;  
4. import android.os.Bundle;  
5. import android.view.View;  
6. import android.view.View.OnClickListener;  
7. import android.widget.Button;  
8. import android.widget.SeekBar;  
9.   
10. public class test_musicplayer extends Activity {  
11.         private Button btnPause, btnPlayUrl, btnStop;  
12.         private SeekBar skbProgress;  
13.         private Player player;  
14.   
15.         /** Called when the activity is first created. */  
16.         @Override  
17.         public void onCreate(Bundle savedInstanceState) {  
18.                 super.onCreate(savedInstanceState);  
19.                 setContentView(R.layout.main);  
20.           
21.                 this.setTitle("在線音樂播放---hellogv編寫");  
22.   
23.                 btnPlayUrl = (Button) this.findViewById(R.id.btnPlayUrl);  
24.                 btnPlayUrl.setOnClickListener(new ClickEvent());  
25.   
26.                 btnPause = (Button) this.findViewById(R.id.btnPause);  
27.                 btnPause.setOnClickListener(new ClickEvent());  
28.   
29.                 btnStop = (Button) this.findViewById(R.id.btnStop);  
30.                 btnStop.setOnClickListener(new ClickEvent());  
31.   
32.                 skbProgress = (SeekBar) this.findViewById(R.id.skbProgress);  
33.                 skbProgress.setOnSeekBarChangeListener(new SeekBarChangeEvent());  
34.                 player = new Player(skbProgress);  
35.   
36.         }  
37.   
38.         class ClickEvent implements OnClickListener {  
39.   
40.                 @Override  
41.                 public void onClick(View arg0) {  
42.                         if (arg0 == btnPause) {  
43.                                 player.pause();  
44.                         } else if (arg0 == btnPlayUrl) {  
45.                                 //在百度MP3裡隨便搜索到的,大家可以試試別的鏈接  
46.                                 String url="http://219.138.125.22/myweb/mp3/CMP3/JH19.MP3";  
47.                                 player.playUrl(url);  
48.                         } else if (arg0 == btnStop) {  
49.                                 player.stop();  
50.                         }  
51.                 }  
52.         }  
53.   
54.         class SeekBarChangeEvent implements SeekBar.OnSeekBarChangeListener {  
55.                 int progress;  
56.   
57.                 @Override  
58.                 public void onProgressChanged(SeekBar seekBar, int progress,  
59.                                 boolean fromUser) {  
60.                         // 原本是(progress/seekBar.getMax())*player.mediaPlayer.getDuration()  
61.                         this.progress = progress * player.mediaPlayer.getDuration()  
62.                                         / seekBar.getMax();  
63.                 }  
64.   
65.                 @Override  
66.                 public void onStartTrackingTouch(SeekBar seekBar) {  
67.   
68.                 }  
69.   
70.                 @Override  
71.                 public void onStopTrackingTouch(SeekBar seekBar) {  
72.                         // seekTo()的參數是相對與影片時間的數字，而不是與seekBar.getMax()相對的數字  
73.                         player.mediaPlayer.seekTo(progress);  
74.                 }  
75.         }  
76.   
77. }