Asynchronous data loading in the list

I have a snippet that contains a ListView . ListView I fill the adapter. In the new Task I fill out the ListView . In the adapter itself, I have to check for emptiness. I need to call a task in the fragment if the list is empty. I implement it like this:

 public class FragmentAddFriends extends Fragment { View v; ListView listView; public ArrayList<myFriend> myFriendArrayList = new ArrayList<>(); ArrayList<String> friendses = new ArrayList<>(); AddFriendsAdapter adapter; ProgressBar progressBar; getAddFriendsTask task; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { v = inflater.inflate(R.layout.add_friends_fragment,container,false); listView = (ListView) v.findViewById(R.id.listViewAddFriends); progressBar = (ProgressBar) v.findViewById(R.id.progressBar2); adapter = new AddFriendsAdapter(getActivity(),myFriendArrayList); listView.setAdapter(adapter); //VKRequest zapros = VKApi.friends().get(VKParameters.from(VKApiConst.OWNER_ID, Integer.parseInt(VKAccessToken.currentToken().userId),VKApiConst.FIELDS,"photo_50")); task = new getAddFriendsTask(); task.execute(); return v; } @Override public void onStop() { super.onStop(); task.cancel(true); } public void update(){ task.execute(); button.setVisibility(View.Visible); } } 

When the method is called again in the fragment, the list is supplemented. That's how I call in the adapter:

 if(list.size()==0){ fragment.update(); } 

But at the same time the method call is made, but the list is not updated. And the button also does not become visible.