1.在xml布局文件中添加SeekBar：

2.在Activity中为SeekBar设置拖动监听器，并更新当前时间：

SeekBar seekBar = (SeekBar) findViewById(R.id.seekBar);
seekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
    int progressChanged = 0;

    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        if(fromUser) {
            mediaPlayer.seekTo(mediaPlayer.getDuration() * progress / 100);
            progressChanged = progress;
        }
    }

    public void onStartTrackingTouch(SeekBar seekBar) {
        // Do something here, if you want to do anything at the start of
        // touching the seekbar
    }

    public void onStopTrackingTouch(SeekBar seekBar) {
        textView.setText(millisecondsToString(mediaPlayer.getCurrentPosition()));
    }
});

3.在Activity中添加一个handler，使用postDelayed方法更新SeekBar和当前时间的UI：

private final Handler mHandler = new Handler();
Runnable mUpdateTimeTask = new Runnable() {
    public void run() {
        long totalDuration = mediaPlayer.getDuration();
        long currentDuration = mediaPlayer.getCurrentPosition();

        // Updating progress bar
        int progress = (int)(getProgressPercentage(currentDuration, totalDuration));
        seekBar.setProgress(progress);

        // Updating current time
        textView.setText(millisecondsToString(currentDuration));

        // Running this thread after 100 milliseconds
        mHandler.postDelayed(this, 100);
    }
};

private double getProgressPercentage(long currentDuration, long totalDuration) {
    Double percentage = (double) 0;

    long currentSeconds = (int) (currentDuration / 1000);
    long totalSeconds = (int) (totalDuration / 1000);

    // Calculating percentage
    percentage =(((double)currentSeconds)/totalSeconds)*100;

    return percentage;
}

private String millisecondsToString(long milliseconds) {
    long minutes = TimeUnit.MILLISECONDS.toMinutes(milliseconds);
    long seconds = TimeUnit.MILLISECONDS.toSeconds(milliseconds)
            - TimeUnit.MINUTES.toSeconds(minutes);

    return String.format("%d:%02d", minutes, seconds);
}

4.在Activity的onCreate方法中启动handler的线程：

// Starting the thread
mHandler.postDelayed(mUpdateTimeTask, 100);

这样就可以实现SeekBar和当前时间的同步更新了。