public class MainActivity extends Activity {

    private MediaPlayer player;
    private SeekBar sb;
    private Timer timer;
    private TimerTask task;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sb = (SeekBar) findViewById(R.id.sb);

        timer = new
 
 Timer();
        task = new TimerTask() {
            public void run() {

                if(player!=null&&player.isPlaying()){
                    //進度條當前位置為音樂的播放位置
                    int CurrentPosition = player.getCurrentPosition();
                    //進度條的最大值為音樂的總長度
                    int
 
 max = player.getDuration();
                    sb.setMax(max);
                    sb.setProgress(CurrentPosition);
                }
            }
        };
        //設定播放時進度條seekbar跟著移動
        timer.schedule(task, 500,500);
        //設定拖拽進度條時，播放音樂改變
        sb.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {

            @Override
 

            public void onStopTrackingTouch(SeekBar seekBar) {
                if( player!=null ){
                    int currentPosition = seekBar.getProgress();
                    player.seekTo(currentPosition);
                }   
            }


            public void onStartTrackingTouch(SeekBar seekBar) {


            }

            public void onProgressChanged(SeekBar seekBar, int progress,
                    boolean fromUser) {

            }
        });
    }

    public void play(View view){

            try {
                if(player==null){
                player = new MediaPlayer();
                player.setAudioStreamType(AudioManager.STREAM_MUSIC);
                player.setDataSource("/mnt/sdcard/a.mp3");
                player.prepare();
                player.start();
                }
            } catch (Exception e) {

                e.printStackTrace();
            } 
    }

    public void pause(View view){
        if(player!=null&&player.isPlaying()){
            player.pause();
        }
    }

    public void resume(View view){
        if(player!=null){
            player.start();
        }
    }

    public void restart(View view){

            try {

                if(player!=null&&player.isPlaying()){
                    player.reset();
                    player.setDataSource("/mnt/sdcard/a.mp3");
                    player.prepare();
                    player.start();
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
    }

    public void stop(View view){
        if(player!=null&&player.isPlaying()){
            player.stop();
            player=null;
        }
    }


    @Override
    protected void onDestroy() {
        if(timer != null && task != null){
            timer.cancel();
            timer = null;
            task.cancel();
            task = null;
        }
        if(player!=null&&player.isPlaying()){
            player.stop();
            player=null;
        }
        super.onDestroy();
    }
}