Как встроить авторизацию через вконтакте?

Суть в том что у меня уже есть готовая авторизация через вк и он работает! А как это всё дело вставить не в классы а в фрагменты? Вот как она выглядит: MainActivity.class

public class MainActivity extends AppCompatActivity {

    private ListView listView;



    ArrayList<String> arrayList = new ArrayList<>();
    ArrayAdapter<String> arrayAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listView = findViewById(R.id.listeners);


        VKSdk.login(this );
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        if (!VKSdk.onActivityResult(requestCode, resultCode, data, new VKCallback<VKAccessToken>() {
            @Override
            public void onResult (VKAccessToken res) {
                VKRequest vkRequest = new VKApiGroups().getById(VKParameters.from("group_ids", "199590682"));
                vkRequest.executeWithListener(new VKRequest.VKRequestListener() {
                    /**
                     * Called if there were no HTTP or API errors, returns execution result.
                     *
                     * @param response response from VKRequest
                     */
                    @Override
                    public void onComplete(VKResponse response) {
                        super.onComplete(response);

                        VKList vkList = (VKList) response.parsedModel;

                        try {

                            VKRequest vkRequest1 = new VKApiWall()
                                    .get(VKParameters.from(VKApiConst.OWNER_ID, "-" + vkList.get(0).fields.getInt("id"), VKApiConst.COUNT, 100));
                            vkRequest1.executeWithListener(new VKRequest.VKRequestListener() {
                                /**
                                 * Called if there were no HTTP or API errors, returns execution result.
                                 *
                                 * @param response response from VKRequest
                                 */
                                @Override
                                public void onComplete(VKResponse response) {
                                    super.onComplete(response);

                                    try {
                                        JSONObject jsonObject = (JSONObject) response.json.get("response");
                                        JSONArray jsonArray = (JSONArray) jsonObject.get("items");

                                        for (int i = 0; i < jsonArray.length(); i++){
                                            JSONObject post = (JSONObject) jsonArray.get(i);
                                            arrayList.add(post.getString("text"));
                                        }
                                        arrayAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, arrayList);
                                        listView.setAdapter(arrayAdapter);
                                    } catch (JSONException e) {
                                        e.printStackTrace();
                                    }
                                }
                            });


                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                });
            }

            @Override
            public void onError(VKError error) {
                Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
            }
        })) {
            super.onActivityResult(requestCode, resultCode, data);
        }
    }
}

Application .class

public class Application extends android.app.Application {

    VKAccessTokenTracker vkAccessTokenTracker = new VKAccessTokenTracker() {
        @Override
        public void onVKAccessTokenChanged(@Nullable VKAccessToken oldToken, @Nullable VKAccessToken newToken) {
            if(newToken == null){
                Intent intent = new Intent(Application.this, MainActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
            }
        }
    };

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

        vkAccessTokenTracker.startTracking();
        VKSdk.initialize(this);
    }
}

Вот как выглядят фрагменты:

NewsFragment

public class NewsFragment extends Fragment {

    private NewsViewModel newsViewModel;

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        newsViewModel =
                ViewModelProviders.of(this).get(NewsViewModel.class);
        View root = inflater.inflate(R.layout.fragment_news, container, false);
        final TextView textView = root.findViewById(R.id.listeners);
        newsViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {
                textView.setText(s);
            }
        });
        return root;
    }
}

NewsViewModel

public class NewsViewModel extends ViewModel {

    private MutableLiveData<String> mText;

    public NewsViewModel() {
        mText = new MutableLiveData<>();
        mText.setValue("На данный момент нет новостей.");
    }

    public LiveData<String> getText() {
        return mText;
    }
}