如何检索此片段中的歌曲列表？

Question

There are two errors neither of which I can figure out why.

1. Cannot resolve method " getContentResolver() "

2.Cannot infer arguments (on the new ArrayAdapter<>() ).

I hope this is the right way to get the songs list from a fragment ? If there is some better alternative, please explain that. Thank you

public class SongsFragment extends Fragment {

    public SongsFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_songs, container, false);
        ListView audioView = (ListView)view.findViewById(R.id.songView);
        ArrayList<String> audioList = new ArrayList<>();
        String[] proj = {MediaStore.Audio.Media._ID, MediaStore.Audio.Media.DISPLAY_NAME};
        final Cursor audioCursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, proj, null, null, null);

        if (audioCursor != null) {
            if (audioCursor.moveToFirst()) {
                do {
                    int audioIndex = audioCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME);

                    audioList.add(audioCursor.getString(audioIndex));
                } while (audioCursor.moveToNext());
            }
        }
        audioCursor.close();

        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, android.R.id.text1, audioList);
        audioView.setAdapter(adapter);

        return view;
    }

}

Answer 1

In class which is extending Fragment Context is not available to get it need to use getActivity() method.

1. Cannot resolve method "getContentResolver()"

Because getContentResolver method is not available in Fragment class, need to user Context to access it:

 final Cursor audioCursor = getActivity().getContentResolver().query(
                              MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, 
                              proj, null, null, null);

2. Cannot infer arguments (on the new ArrayAdapter<>()).

Because ArrayAdapter constructor require valid Context as first parameter :

ArrayAdapter<String> adapter = new ArrayAdapter<>(getActivity(), 
                                         android.R.layout.simple_list_item_1, 
                                         android.R.id.text1, audioList);