After fixing 4 errors in NumbersFragment.java

onCreateView() method in NumbersFragment.java

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

   // Create and setup the {@link AudioManager} to request audio focus
   mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

   // Create a list of words
   final ArrayList<Word> words = new ArrayList<Word>();
   words.add(new Word(R.string.number_one, R.string.miwok_number_one,
           R.drawable.number_one, R.raw.number_one));
   words.add(new Word(R.string.number_two, R.string.miwok_number_two,
           R.drawable.number_two, R.raw.number_two));
   words.add(new Word(R.string.number_three, R.string.miwok_number_three,
           R.drawable.number_three, R.raw.number_three));
   words.add(new Word(R.string.number_four, R.string.miwok_number_four,
           R.drawable.number_four, R.raw.number_four));
   words.add(new Word(R.string.number_five, R.string.miwok_number_five,
           R.drawable.number_five, R.raw.number_five));
   words.add(new Word(R.string.number_six, R.string.miwok_number_six,
           R.drawable.number_six, R.raw.number_six));
   words.add(new Word(R.string.number_seven, R.string.miwok_number_seven,
           R.drawable.number_seven, R.raw.number_seven));
   words.add(new Word(R.string.number_eight, R.string.miwok_number_eight,
           R.drawable.number_eight, R.raw.number_eight));
   words.add(new Word(R.string.number_nine, R.string.miwok_number_nine,
           R.drawable.number_nine, R.raw.number_nine));
   words.add(new Word(R.string.number_ten, R.string.miwok_number_ten,
           R.drawable.number_ten, R.raw.number_ten));

   // Create an {@link WordAdapter}, whose data source is a list of {@link Word}s. The
   // adapter knows how to create list items for each item in the list.
   WordAdapter adapter = new WordAdapter(this, words, R.color.category_numbers);

   // Find the {@link ListView} object in the view hierarchy of the {@link Activity}.
   // There should be a {@link ListView} with the view ID called list, which is declared in the
   // word_list.xml layout file.
   ListView listView = (ListView) findViewById(R.id.list);

   // Make the {@link ListView} use the {@link WordAdapter} we created above, so that the
   // {@link ListView} will display list items for each {@link Word} in the list.
   listView.setAdapter(adapter);

   // Set a click listener to play the audio when the list item is clicked on
   listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
       @Override
       public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
           // Release the media player if it currently exists because we are about to
           // play a different sound file
           releaseMediaPlayer();

           // Get the {@link Word} object at the given position the user clicked on
           Word word = words.get(position);

           // Request audio focus so in order to play the audio file. The app needs to play a
           // short audio file, so we will request audio focus with a short amount of time
           // with AUDIOFOCUS_GAIN_TRANSIENT.
           int result = mAudioManager.requestAudioFocus(mOnAudioFocusChangeListener,
                   AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);

           if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
               // We have audio focus now.

               // Create and setup the {@link MediaPlayer} for the audio resource associated
               // with the current word
               mMediaPlayer = MediaPlayer.create(NumbersActivity.this, word.getAudioResourceId());

               // Start the audio file
               mMediaPlayer.start();

               // Setup a listener on the media player, so that we can stop and release the
               // media player once the sound has finished playing.
               mMediaPlayer.setOnCompletionListener(mCompletionListener);
           }
       }
   });
}