Android MusicPlayer 4

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private Button playBtn;
    private SeekBar positionBar;
    private SeekBar volumeBar;
    private TextView elapsedTimeLabel;
    private TextView remainingTimeLabel;
    private MediaPlayer mp;
    private int totalTime;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        playBtn = findViewById(R.id.playBtn);
        elapsedTimeLabel = findViewById(R.id.elapsedTimeLabel);
        remainingTimeLabel = findViewById(R.id.remainingTimeLabel);

        // Media Playerの初期化
        mp = MediaPlayer.create(this, R.raw.music);
        mp.setLooping(true);
        mp.seekTo(0);
        mp.setVolume(0.5f, 0.5f);
        totalTime = mp.getDuration();