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

}