Android MusicPlayer 5

MainActivity.java

    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            int currentPosition = msg.what;

            // 再生位置を更新
            positionBar.setProgress(currentPosition);

            // 経過時間ラベル更新
            String elapsedTime = createTimeLabel(currentPosition);
            elapsedTimeLabel.setText(elapsedTime);

            // 残り時間ラベル更新
            String remainingTime = createTimeLabel(totalTime-currentPosition);
            remainingTimeLabel.setText("- " + remainingTime);
        }
    };

    public String createTimeLabel(int time) {
        String timeLabel = "";
        int min = time / 1000 / 60;
        int sec = time / 1000 % 60;

        timeLabel = min + ":";
        if (sec < 10) timeLabel += "0";
        timeLabel += sec;

        return timeLabel;
    }

    public void playBtnClick(View view) {
        if (!mp.isPlaying()) {