Android音量seekbar制作

很多音乐播放器界面上都有一个音量seekbar，那么在android里面是如何实现的呢？

 　　首先分析下要解决的问题：1.获取媒体播放的音量。

　　　　　　　　　　　　　　 2.通过seekbar可以增减音量

　　　　　　　　　　　　　　 3.用户按下音量键增减音量，seekbar保持同步

　　　对于第一个问题：Android系统提供AudioManager类来获得系统audio服务。

　　　对于第二个问题：实现seekBarChangeLIstener里面onProgressChanged方法。

　　　 对于第三个问题：用线程来同步更新UI。

　　　设置音量的代码：

  
    

   
     1 
   
     private
   
      
   
     void
   
      setVolum()

   
     2 
   
      {

   
     3 
   
      

   
     4 
   
      maxVolume 
   
     =
   
      mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);

   
     5 
   
      volSeekBar.setMax(maxVolume);

   
     6 
   
      currentVolume 
   
     =
   
      mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);

   
     7 
   
      volSeekBar.setProgress(currentVolume);

   
     8 
   
      mVolume.setText(currentVolume
   
     *
   
     100
   
     /
   
     maxVolume 
   
     +
   
      
   
     "
   
      
   
     "
   
     );

   
     9 
   
      }
  
    

  　　实现seekbar控制音量代码：

  
    

   
     OnSeekBarChangeListener seekBarChangeListener 
   
     =
   
      
   
     new
   
      OnSeekBarChangeListener()
 {

 
   
     public
   
      
   
     void
   
      onProgressChanged(SeekBar seekBar, 
   
     int
   
      progress,
 
   
     boolean
   
      fromUser) {
 
   
     //
   
      TODO Auto-generated method stub
   
     

   
      mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, progress, 
   
     0
   
     );
 }

 
   
     public
   
      
   
     void
   
      onStartTrackingTouch(SeekBar seekBar) {
 
   
     //
   
      TODO Auto-generated method stub
   
     

   
      
 }

 
   
     public
   
      
   
     void
   
      onStopTrackingTouch(SeekBar seekBar) {
 
   
     //
   
      TODO Auto-generated method stub
   
     

   
      
 }
 
 };
  
    

　　　　线程更新UI代码：

  
    

   
      1 
   
     Handler myHandler 
   
     =
   
      
   
     new
   
      Handler(){

   
      2 
   
      
   
     public
   
      
   
     void
   
      handleMessage(Message msg) { 

   
      3 
   
      
   
     switch
   
      (msg.what) { 

   
      4 
   
      
   
     case
   
      PROGRESS_CHANGED: 

   
      5 
   
      setVolum(); 

   
      6 
   
      
   
     /*
   
     sendEmptyMessageDelayed(PROGRESS_CHANGED, 200);
   
     */
   
     

   
      7 
   
      
   
     break
   
     ;

   
      8 
   
      }

   
      9 
   
      }

   
     10 
   
      };

   
     11 
   
     

   
     12 
   
      
   
     class
   
      myVolThread 
   
     implements
   
      Runnable { 

   
     13 
   
      
   
     public
   
      
   
     void
   
      run() { 

   
     14 
   
      
   
     while
   
      (
   
     !
   
     Thread.currentThread().isInterrupted()) { 

   
     15 
   
      

   
     16 
   
      Message message 
   
     =
   
      
   
     new
   
      Message(); 

   
     17 
   
      message.what 
   
     =
   
     PROGRESS_CHANGED; 

   
     18 
   
      MainActivity.
   
     this
   
     .myHandler.sendMessage(message); 

   
     19 
   
      
   
     try
   
      { 

   
     20 
   
      Thread.sleep(
   
     100
   
     ); 

   
     21 
   
      } 
   
     catch
   
      (InterruptedException e) { 

   
     22 
   
      Thread.currentThread().interrupt(); 

   
     23 
   
      } 

   
     24 
   
      } 

   
     25 
   
      } 

   
     26 
   
      } 
  
    

  最后贴上MainActivity代码：

01 public class MainActivity extends Activity {
02
03     protected static final int PROGRESS_CHANGED = 0x101;
04     private SeekBar volSeekBar ;
05     private TextView mVolume ;
06     private AudioManager mAudioManager;
07     private int maxVolume, currentVolume;
08
09     Thread myVolThread = null;
10     Handler myHandler = new Handler(){
11         public void handleMessage(Message msg) {
12             switch (msg.what) {
13             case PROGRESS_CHANGED:
14                 setVolum();
15                 /*sendEmptyMessageDelayed(PROGRESS_CHANGED, 200);*/
16                 break;
17            }
18         }
19     };
20     public void onCreate(Bundle savedInstanceState) {
21         super.onCreate(savedInstanceState);
22         setContentView(R.layout.main);
23
24         volSeekBar= (SeekBar)findViewById(R.id.volum_seek);
25         mVolume = (TextView)findViewById(R.id.volum_val);
26         mAudioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);
27
28         //setVolum();
29         OnSeekBarChangeListener seekBarChangeListener = new OnSeekBarChangeListener()
30         {
31
32             public void onProgressChanged(SeekBar seekBar, int progress,
33                     boolean fromUser) {
34                 // TODO Auto-generated method stub
35                 mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, progress, 0);
36             }
37
38             public void onStartTrackingTouch(SeekBar seekBar) {
39                 // TODO Auto-generated method stub
40
41             }
42
43             public void onStopTrackingTouch(SeekBar seekBar) {
44                 // TODO Auto-generated method stub
45
46             }
47
48         };
49
50         volSeekBar.setOnSeekBarChangeListener(seekBarChangeListener);
51         new Thread(new myVolThread()).start();
52
53     }
54     private void setVolum()
55     {
56
57         maxVolume = mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
58         volSeekBar.setMax(maxVolume);
59         currentVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
60         volSeekBar.setProgress(currentVolume);
61         mVolume.setText(currentVolume*100/maxVolume + " ");
62     }
63
64     class myVolThread implements Runnable {
65         public void run() {
66              while (!Thread.currentThread().isInterrupted()) {
67
68                   Message message = new Message();
69                   message.what =PROGRESS_CHANGED;
70                   MainActivity.this.myHandler.sendMessage(message);
71                   try {
72                        Thread.sleep(100);
73                   } catch (InterruptedException e) {
74                        Thread.currentThread().interrupt();
75                   }
76              }
77         }
78    }
79 }