實現音樂播放器，多線程處理進度條

	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		File musicDir=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
		file=new File(musicDir,"朴樹 - 白樺林.mp3");
		seekBar=(SeekBar) findViewById(R.id.seekBar1);
		currentTv=(TextView) findViewById(R.id.TextView01);
		durationTv=(TextView) findViewById(R.id.TextView02);
		seekBar.setOnSeekBarChangeListener(this);
		mHandler=new MainHandler();//默認當前線程Looper
	}
	enum States{STOP,PAUSE}
	States state=States.STOP;
	private MediaPlayer mPlayer;
	private SeekBarThread barThread;


	/**實現音樂的播放*/
	public void onMusicPlay(View v){
		//判定播放器對象是否爲空，爲null則創建新的對象
		if(mPlayer==null){
			mPlayer=new MediaPlayer();
			mPlayer.setOnPreparedListener(this);
			mPlayer.setOnCompletionListener(this);
		}
		//判定媒體播放狀態，假如是暫停則直接啓動播放
		if(state==States.PAUSE){
			mPlayer.start();
			return;
		}
		//假如不是暫停狀態則設置要播放的音樂路徑，加載音樂
		try{
			mPlayer.setDataSource(file.getPath());
			mPlayer.prepareAsync();//工作線程加載
		}catch(Exception e){e.printStackTrace();}
		//更新seekBar
		if(barThread==null){
			barThread=new SeekBarThread();
			barThread.start();
		}
	}
	private boolean isUpdate=true;
	/**負責給主線程發消息，更新SeekBar的線程對象*/
	class SeekBarThread extends Thread{
		@Override
		public void run() {
			while(isUpdate){
				try{sleep(1000);}catch(Exception e){}
				mHandler.sendEmptyMessage(1);
			}
		}
	}
	/**實現進度條*/
	private SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
	class MainHandler extends Handler{
		public MainHandler() {}
		public MainHandler(Looper looper) {super(looper);}
		@Override
		public void handleMessage(Message msg) {
			if(msg.what==1&&mPlayer!=null){
				int cPos=mPlayer.getCurrentPosition();//獲取當前位置 
				seekBar.setProgress(cPos);//setMax是設置 進度條的最大值,setProgress是設置進度條的當前進度。
			}
		}
	}
	/**實現音樂的暫停*/
	public void onMusicPause(View v){
		if(mPlayer!=null&&mPlayer.isPlaying()){
			mPlayer.pause();
			state=States.PAUSE;
		}
	}
	@Override
	protected void onDestroy() {
		super.onDestroy();
		isUpdate=false;
		if(mPlayer!=null){
			mPlayer.release();
			mPlayer=null;
		}
	}
	/**當音樂加載完成以後會執行此方法*/
	@Override
	public void onPrepared(MediaPlayer mp) {
		Log.i("TAG", "onPrepared");
		mp.start();
		//getDuration()獲取歌曲長度，毫秒
		durationTv.setText(sdf.format(new Date(mPlayer.getDuration())));
		seekBar.setMax(mPlayer.getDuration());
	}
	@Override
	public void onCompletion(MediaPlayer mp) {//Completion 結束
		Log.i("TAG", "onCompletion");
		mp.start();
	}
	/**以下是設置seekBar監聽，實現接口後自動添加的*/
	@Override
	public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
		currentTv.setText(sdf.format(new Date(mPlayer.getCurrentPosition())));
	}
	@Override
	public void onStartTrackingTouch(SeekBar seekBar) {
		// TODO Auto-generated method stub
	}
	@Override
	public void onStopTrackingTouch(SeekBar seekBar) {
		if(mPlayer!=null){
			int cPos=seekBar.getProgress();
			//實現跳轉到要播放的位置的功能！
			mPlayer.seekTo(cPos);
		}
	}