Why cant I observe data with viewmodel as LifecycleOwner?

Question

I load my data using an AsyncTask in my ViewModel but when i try to observe the data inside my fragment then i get the exception:
Caused by: java.lang.ClassCastException: MainFragment cannot be cast to android.arch.lifecycle.LifecycleOwner

This is my ViewModel:

private MutableLiveData<ArrayList<Song>> songs;
public LiveData<ArrayList<Song>> getSongs() {
    if (songs == null) {
        songs = new MutableLiveData<ArrayList<Song>>();
        loadSongs();
    }
    return songs;
}

@SuppressLint("StaticFieldLeak")
private void loadSongs() {

    new AsyncTask<Void, Void, ArrayList<Song>>() {
        @Override
        protected ArrayList<Song> doInBackground(Void... voids) {
            ArrayList<Song> data = new ArrayList<>();

            //Add songs (collapsed)

            return data;
        }

        @Override
        protected void onPostExecute(ArrayList<Song> data) {
            songs.postValue(data);
        }
    }.execute();
}

And this is my fragment where i want my data inside my listview:

viewModel = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);

    //TODO: Fix this!
    viewModel.getSongs().observe((LifecycleOwner) this, new Observer<ArrayList<Song>>() {
        @Override
        public void onChanged(@Nullable ArrayList<Song> songs) {
            adapter = new ListViewAdapter(R.layout.songlist_customlayout, viewModel.getSongs().getValue(), getActivity());
        }
    });

What is the problem here?

Answer 1

I fixed the ClassCastException by migrating my project to androidx. Now i dont get the error anymore :)