播放音乐 上下播放

public class MainActivity extends Activity {    private MediaPlayer player;    private MediaPlayer players;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    //第二种方法  添加到sdcard    //播放    public void Plays(View v){        players = new MediaPlayer();        players.setAudioStreamType(AudioManager.STREAM_MUSIC);//        try {            players.setDataSource("/sdcard/people.mp3");            players.prepare();            players.start();        } catch (Exception e) {            e.printStackTrace();        }    }    //暂停    public void pause(View v){        if (players != null && players.isPlaying()) {            players.pause();        }else{            players.start();        }    }    //停止    public void Stop(View v){        if (players != null && players.isPlaying()) {            players.stop();            players.release();//释放资源            players=null;        }    }}                     //实现上一首，下一首                  public class MainActivity extends Activity {    private MediaPlayer player;    private List<String> asList;    private int count = 0;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        asList = Arrays.asList("/sdcard/ifyou.mp3","/sdcard/people.mp3");    }    public void Play(int count) {        try {            player = new MediaPlayer();            player.setAudioStreamType(AudioManager.STREAM_MUSIC);            player.setDataSource(asList.get(count));            player.prepare();            player.start();        } catch (Exception e) {            e.printStackTrace();        }    }    // 播放    public void Action(View v) {         Play(count);    }    // 上一首    public void Last(View v) {        if (player != null && player.isPlaying()) {            if (count <= 0) {                Toast.makeText(MainActivity.this, "这是第一首", 0).show();            } else {                count--;                Stop();                Play(count);            }        }    }    // 下一首    public void Naxt(View v) {        if (player != null && player.isPlaying()) {            if (count < (asList.size()-1)) {                count++;                Stop();                Play(count);            } else {                Toast.makeText(MainActivity.this, "这是最后一首", 0).show();            }        }    }    public void Stop() {        if (player != null && player.isPlaying()) {            player.stop();            player.release();            player=null;        }    }}