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：

view source print ?

`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 }

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