Android提高21篇之一：MediaPlayer

       本文介紹MediaPlayer的使用。MediaPlayer可以播放音頻和視頻，另外也可以通過VideoView來播放視頻，雖然VideoView比MediaPlayer簡單易用，但定制性不如用MediaPlayer，要視情況選擇了。MediaPlayer播放音頻比較簡單，但是要播放視頻就需要SurfaceView。SurfaceView比普通的自定義View更有繪圖上的優勢，它支持完全的OpenGL ES庫。

       先貼出本文程序運行結果的截圖，上面是播放/停止音頻，可用SeekBar來調進度，下面是播放/停止視頻，也是用SeekBar來調進度：

       main.xml的源碼：

1. <linearlayout android:id="@+id/LinearLayout01"   
2.         android:layout_width="fill_parent" android:layout_height="fill_parent"  
3.         xmlns:android="http://schemas.android.com/apk/res/android"  
4.         android:orientation="vertical">  
5.         <seekbar android:id="@+id/SeekBar01" android:layout_height="wrap_content"   
6.                 android:layout_width="fill_parent">  
7.         <linearlayout android:id="@+id/LinearLayout02"   
8.                 android:layout_width="wrap_content" android:layout_height="wrap_content">  
9.                 <button android:id="@+id/Button01" android:layout_width="wrap_content"   
10.                         android:layout_height="wrap_content" android:text="播放音頻">  
11.                 <button android:id="@+id/Button02" android:layout_width="wrap_content"   
12.                         android:layout_height="wrap_content" android:text="停止播放">  
13.           
14.         <seekbar android:id="@+id/SeekBar02" android:layout_height="wrap_content"   
15.                 android:layout_width="fill_parent">  
16.   
17.         <surfaceview android:id="@+id/SurfaceView01"   
18.                 android:layout_width="fill_parent" android:layout_height="250px">  
19.         <linearlayout android:id="@+id/LinearLayout02"   
20.                 android:layout_width="wrap_content" android:layout_height="wrap_content">  
21.                 <button android:layout_width="wrap_content"   
22.                         android:layout_height="wrap_content" android:id="@+id/Button03"  
23.                         android:text="播放視頻">  
24.                 <button android:layout_width="wrap_content"   
25.                         android:layout_height="wrap_content" android:text="停止播放" android:id="@+id/Button04">  

       本文程序的源碼，有點長：

1. package com.testMedia;  
2.   
3. import java.io.IOException;    
4. import java.util.Timer;  
5. import java.util.TimerTask;  
6. import android.app.Activity;    
7. import android.media.AudioManager;  
8. import android.media.MediaPlayer;  
9. import android.os.Bundle;    
10. import android.view.SurfaceHolder;  
11. import android.view.SurfaceView;  
12. import android.view.View;    
13. import android.widget.Button;    
14. import android.widget.SeekBar;  
15. import android.widget.Toast;    
16.   
17.   
18. public class testMedia extends Activity {  
19.           /** Called when the activity is first created. */   
20.   
21.         private SeekBar skb_audio=null;  
22.     private Button btn_start_audio = null;    
23.     private Button btn_stop_audio = null;  
24.   
25.     private SeekBar skb_video=null;  
26.     private Button btn_start_video = null;    
27.     private Button btn_stop_video = null;  
28.     private SurfaceView surfaceView;   
29.     private SurfaceHolder surfaceHolder;   
30.       
31.     private MediaPlayer m = null;    
32.     private Timer mTimer;  
33.     private TimerTask mTimerTask;  
34.       
35.     private boolean isChanging=false;//互斥變量，防止定時器與SeekBar拖動時進度沖突  
36.      @Override    
37.     public void onCreate(Bundle savedInstanceState) {    
38.         super.onCreate(savedInstanceState);    
39.         setContentView(R.layout.main);    
40.           
41.         //----------Media控件設置---------//  
42.         m=new MediaPlayer();  
43.           
44.         //播放結束之後彈出提示  
45.         m.setOnCompletionListener(new MediaPlayer.OnCompletionListener(){  
46.                         @Override  
47.                         public void onCompletion(MediaPlayer arg0) {  
48.                                 Toast.makeText(testMedia.this, "結束", 1000).show();  
49.                                 m.release();  
50.                         }  
51.         });  
52.           
53.       //----------定時器記錄播放進度---------//  
54.         mTimer = new Timer();  
55.         mTimerTask = new TimerTask() {  
56.             @Override  
57.             public void run() {          
58.                     if(isChanging==true)  
59.                             return;  
60.                       
61.                     if(m.getVideoHeight()==0)  
62.                             skb_audio.setProgress(m.getCurrentPosition());  
63.                     else   
64.                             skb_video.setProgress(m.getCurrentPosition());  
65.             }  
66.         };  
67.   
68.         mTimer.schedule(mTimerTask, 0, 10);  
69.                   
70.         btn_start_audio = (Button) this.findViewById(R.id.Button01);    
71.         btn_stop_audio = (Button) this.findViewById(R.id.Button02);    
72.         btn_start_audio.setOnClickListener(new ClickEvent());  
73.         btn_stop_audio.setOnClickListener(new ClickEvent());  
74.         skb_audio=(SeekBar)this.findViewById(R.id.SeekBar01);  
75.         skb_audio.setOnSeekBarChangeListener(new SeekBarChangeEvent());  
76.           
77.         btn_start_video = (Button) this.findViewById(R.id.Button03);    
78.         btn_stop_video = (Button) this.findViewById(R.id.Button04);    
79.         btn_start_video.setOnClickListener(new ClickEvent());  
80.         btn_stop_video.setOnClickListener(new ClickEvent());  
81.         skb_video=(SeekBar)this.findViewById(R.id.SeekBar02);  
82.         skb_video.setOnSeekBarChangeListener(new SeekBarChangeEvent());  
83.         surfaceView = (SurfaceView) findViewById(R.id.SurfaceView01);  
84.         surfaceHolder = surfaceView.getHolder();  
85.         surfaceHolder.setFixedSize(100, 100);  
86.         surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);  
87.     }    
88.        
89.   /* 
90.    * 按鍵事件處理 
91.    */  
92.   class ClickEvent implements View.OnClickListener{  
93.         @Override  
94.         public void onClick(View v) {  
95.                 if(v==btn_start_audio)  
96.                 {  
97.                         m.reset();//恢復到未初始化的狀態  
98.                         m=MediaPlayer.create(testMedia.this, R.raw.big);//讀取音頻  
99.                         skb_audio.setMax(m.getDuration());//設置SeekBar的長度  
100.                         try {                                          
101.                                 m.prepare();        //准備  
102.                         } catch (IllegalStateException e) {                          
103.                                 // TODO Auto-generated catch block                                  
104.                                 e.printStackTrace();                                  
105.                         } catch (IOException e) {                          
106.                                 // TODO Auto-generated catch block                                  
107.                                 e.printStackTrace();                                  
108.                         }                  
109.                         m.start();        //播放  
110.                 }  
111.                 else if(v==btn_stop_audio || v==btn_stop_video)  
112.                 {  
113.                         m.stop();  
114.                 }  
115.                 else if(v==btn_start_video)  
116.                 {  
117.                         m.reset();//恢復到未初始化的狀態  
118.                         m=MediaPlayer.create(testMedia.this, R.raw.test);//讀取視頻  
119.                         skb_video.setMax(m.getDuration());//設置SeekBar的長度  
120.                         m.setAudioStreamType(AudioManager.STREAM_MUSIC);  
121.                         m.setDisplay(surfaceHolder);//設置屏幕  
122.                           
123.                         try {  
124.                             m.prepare();  
125.                               
126.                         } catch (IllegalArgumentException e) {  
127.                                 // TODO Auto-generated catch block  
128.                                 e.printStackTrace();  
129.                         } catch (IllegalStateException e) {  
130.                                 // TODO Auto-generated catch block  
131.                                 e.printStackTrace();  
132.                         } catch (IOException e) {  
133.                                 // TODO Auto-generated catch block  
134.                                 e.printStackTrace();  
135.                         }  
136.                         m.start();  
137.                 }  
138.         }  
139.   }  
140.     
141.   /* 
142.    * SeekBar進度改變事件 
143.    */  
144.   class SeekBarChangeEvent implements SeekBar.OnSeekBarChangeListener{  
145.   
146.         @Override  
147.         public void onProgressChanged(SeekBar seekBar, int progress,  
148.                         boolean fromUser) {  
149.                 // TODO Auto-generated method stub  
150.                   
151.         }  
152.   
153.         @Override  
154.         public void onStartTrackingTouch(SeekBar seekBar) {  
155.             isChanging=true;  
156.         }  
157.   
158.         @Override  
159.         public void onStopTrackingTouch(SeekBar seekBar) {  
160.                 m.seekTo(seekBar.getProgress());  
161.             isChanging=false;          
162.         }  
163.             
164.   }  
165.   
166. }