尝试在Media Player Fragment上获取null数组的长度

Question

   // BUTTONS
private ImageButton btnPlay;
private ImageButton btnForward;
private ImageButton btnBackward;
private ImageButton btnNext;
private ImageButton btnPrevious;
private ImageButton btnPlaylist;
private ImageButton btnRepeat;
private ImageButton btnShuffle;
private SeekBar songProgressBar;
private TextView songTitleLabel;
private TextView songCurrentDurationLabel;
private TextView songTotalDurationLabel;

// MEDIA PLAYER
private  MediaPlayer mp;

// HANDLER TO UPDATE UI TIMER, PROGRESS BAR
private Handler mHandler = new Handler();;
private SongsManager songManager;
private Utilities utils;
private int seekForwardTime = 5000; // 5000 milliseconds
private int seekBackwardTime = 5000; // 5000 milliseconds
private int currentSongIndex = 0;
private boolean isShuffle = false;
private boolean isRepeat = false;
private ArrayList<HashMap<String, String>> songsList = new 
ArrayList<HashMap<String, String>>();


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.tab3_soundfragment, container, false);




/**
 * Receiving song index from playlist view
 * and play the song
 * */
@Override
public void onActivityResult(int requestCode,
                                int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(resultCode == 100){
        currentSongIndex = data.getExtras().getInt("songIndex");
        // play selected song
        playSong(currentSongIndex);
    }

}

/**
 * Function to play a song
 * @param songIndex - index of song
 * */
public void  playSong(int songIndex){
    // Play song
    try {
        mp.reset();
        mp.setDataSource(songsList.get(songIndex).get("songPath"));
        mp.prepare();
        mp.start();
        // Displaying Song title
        String songTitle = songsList.get(songIndex).get("songTitle");
        songTitleLabel.setText(songTitle);

        // Changing Button Image to pause image
        btnPlay.setImageResource(R.drawable.btn_pause);

        // set Progress bar values
        songProgressBar.setProgress(0);
        songProgressBar.setMax(100);

        // Updating progress bar
        updateProgressBar();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

/*
 * Update timer on seekbar
 */
public void updateProgressBar() {
    mHandler.postDelayed(mUpdateTimeTask, 100);
}

/*
 * Background Runnable thread
 */
private Runnable mUpdateTimeTask = new Runnable() {
    public void run() {
        long totalDuration = mp.getDuration();
        long currentDuration = mp.getCurrentPosition();

        // Displaying Total Duration time
        songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration));
        // Displaying time completed playing
        songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration));

        // Updating progress bar
        int progress = (int)(utils.getProgressPercentage(currentDuration, totalDuration));
        //Log.d("Progress", ""+progress);
        songProgressBar.setProgress(progress);

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

/*
 *
 */
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) {

}

/*
 * When user starts moving the progress handler
 */
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
    // remove message Handler from updating progress bar
    mHandler.removeCallbacks(mUpdateTimeTask);
}

/*
 * When user stops moving the progress hanlder
 */
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
    mHandler.removeCallbacks(mUpdateTimeTask);
    int totalDuration = mp.getDuration();
    int currentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration);

    // forward or backward to certain seconds
    mp.seekTo(currentPosition);

    // update timer progress again
    updateProgressBar();
}

/**
 * On Song Playing completed
 * if repeat is ON play same song again
 * if shuffle is ON play random song
 * */
@Override
public void onCompletion(MediaPlayer arg0) {

    // check for repeat is ON or OFF
    if(isRepeat){
        // repeat is on play same song again
        playSong(currentSongIndex);
    } else if(isShuffle){
        // shuffle is on - play a random song
        Random rand = new Random();
        currentSongIndex = rand.nextInt((songsList.size() - 1) - 0 + 1) + 0;
        playSong(currentSongIndex);
    } else{
        // no repeat or shuffle ON - play next song
        if(currentSongIndex < (songsList.size() - 1)){
            playSong(currentSongIndex + 1);
            currentSongIndex = currentSongIndex + 1;
        }else{
            // play first song
            playSong(0);
            currentSongIndex = 0;
        }
    }
}

我得到错误java.lang.NullPointerException：尝试获取null数组的长度

我在Android开发方面有点新鲜，如果有人可以帮助我，我会感激不尽。

我试图从网址获取音乐但是当我这样做时，这给了我这个错误