如何在Android中的微调器onItemSelected上刷新片段

Question

I have a fragment with a spinner and a listview the list view is updated when the user chooses one of the options from the spinner, and I came to an idea that I have to refresh the fragment when an option is chosen. but the issue is the fragment goes in an infinity loop when I refresh the fragment from "onItemSelected" so I made a "refreshFragment method" to solve the issue but now after the user chooses an option the first option from the spinner don't refresh the fragment again, all the other options working well except the first one because I didn't add the "refreshFragment method" in to this option because if I add it it will go to the infinity loop again. sorry for my bad English I always get down votes because of that.

    public class MatchesFragment extends Fragment implements SwipeRefreshLayout.OnRefreshListener, AdapterView.OnItemSelectedListener {

        private RecyclerView recyclerView;
        private MatchAdapter matchAdapter;
        private ArrayList<Matches> matchCollection;
        SwipeRefreshLayout mSwipeRefreshLayout;

        String apiLink;
        String apiType = "1";


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

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


        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            // Inflate the layout for this fragment
            return inflater.inflate(R.layout.fragment_matches, container, false);
        }

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

            mSwipeRefreshLayout = (SwipeRefreshLayout) getView().findViewById(R.id.swiperefresh);
            mSwipeRefreshLayout.setOnRefreshListener(this);


            if (getArguments() != null) {
                Bundle arguments = getArguments();
                apiLink = arguments.getString("ApiLink");
                apiType = arguments.getString("apiType");
                Toast.makeText(getContext().getApplicationContext(), apiType, Toast.LENGTH_LONG).show();
            }else {
                apiLink = "http://first-api-link";
                Toast.makeText(getContext().getApplicationContext(), "nothing", Toast.LENGTH_LONG).show();
            }

            Spinner spinner = (Spinner) getView().findViewById(R.id.spinner);
            spinner.setOnItemSelectedListener(this);

    // Create an ArrayAdapter using the string array and a default spinner layout
            ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(getActivity(),
                    R.array.planets_array, android.R.layout.simple_spinner_item);
    // Specify the layout to use when the list of choices appears
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    // Apply the adapter to the spinner
            spinner.setAdapter(adapter);

            ConnectivityManager cm = (ConnectivityManager) getContext().getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);

            NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
            String answer = "Internet";
            if (null != activeNetwork) {
                if(activeNetwork.getType() == ConnectivityManager.TYPE_WIFI)
                    answer="You are connected to a WiFi Network";
                if(activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE)
                    answer="You are connected to a Mobile Network";
                init();
                new FetchDataTask().execute();
            }
            else {
                answer = "No internet Connectivity";
                Toast.makeText(getContext().getApplicationContext(), answer, Toast.LENGTH_LONG).show();
            }
        }

        private void init() {
            recyclerView = (RecyclerView) getActivity().findViewById(R.id.matchesRecyclerview);
            recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
            recyclerView.setHasFixedSize(true);
            matchCollection = new ArrayList<>();
            matchAdapter = new MatchAdapter(matchCollection, getActivity());
            recyclerView.setAdapter(matchAdapter);
        }

        @Override
        public void onRefresh() {
            init();
            new FetchDataTask().execute();
        }

        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            apiLink = "http://first-api-link";
            switch (position){
//can't add refreshFragment in here it makes infinity lopp
                case 0: apiLink = "first-api-link";
                break;
                case 1:
                    refreshFragment("second-api-link", 2);
                break;
                case 2:
                    refreshFragment("third-api-link", 3);
                    break;
                case 3:
                    refreshFragment("fourth-api-link", 4);
                    break;
                case 4:
                    refreshFragment("fifth-api-link", 5);
                    break;
                case 5:
                    refreshFragment("sixth-api-link", 6);
                    break;
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }

        public class FetchDataTask extends AsyncTask<Void, Void, Void> {
            private String mZomatoString;

            @Override
            protected Void doInBackground(Void... params) {
                HttpURLConnection urlConnection = null;
                BufferedReader reader = null;
                Uri builtUri = Uri.parse(apiLink);
                URL url;
                try {
                    url = new URL(builtUri.toString());
                    urlConnection = (HttpURLConnection) url.openConnection();
                    urlConnection.setRequestMethod("GET");
                    urlConnection.setRequestProperty("user-key", "acfd3e623c5f01289bd87aaaff1926c1");
                    urlConnection.connect();

                    InputStream inputStream = urlConnection.getInputStream();
                    StringBuffer buffer = new StringBuffer();
                    if (inputStream == null) {
                        //Nothing to do
                        return null;
                    }

                    reader = new BufferedReader(new InputStreamReader(inputStream));

                    String line;
                    while ((line = reader.readLine()) != null) {
                        buffer.append(line + "\n");
                    }

                    if (buffer.length() == 0) {
                        return null;
                    }

                    mZomatoString = buffer.toString();
                    JSONObject jsonObject = new JSONObject(mZomatoString);

                    Log.v("Response", jsonObject.toString());

                    JSONArray matchArray = jsonObject.getJSONArray("data");


                    //list = new ArrayList<>();
                    for (int i = 0; i < matchArray.length(); i++) {

                        Log.v("BRAD_", i + "");
                        String home_team;
                        String away_team;
                        String home_flag;
                        String away_flag;

                        JSONObject jTeam = (JSONObject) matchArray.get(i);

                        if (apiType == "1"){
                        JSONObject jHomeTeam = (JSONObject) jTeam.getJSONObject("home_team");
                        JSONObject jAwayTeam = (JSONObject) jTeam.getJSONObject("away_team");

                        //get data's from json sent from link
                        home_team = jHomeTeam.getString("name");
                        away_team = jAwayTeam.getString("name");
                        home_flag = jHomeTeam.getString("flag");
                        away_flag = jAwayTeam.getString("flag");
                        }else{
                            //get data's from json sent from link
                            home_team = jTeam.getString("home_team");
                            away_team = jTeam.getString("away_team");
                            home_flag = "https://www.countries-ofthe-world.com/flags-normal/flag-of-Russia.png";
                            away_flag = "https://www.countries-ofthe-world.com/flags-normal/flag-of-Russia.png";
                        }



                        Matches matches = new Matches();
                        matches.setHome_team(home_team);
                        matches.setAway_team(away_team);
                        matches.setHome_flag(home_flag);
                        matches.setAway_flag(away_flag);

                        matchCollection.add(matches);
                        // Stopping swipe refresh
                        mSwipeRefreshLayout.setRefreshing(false);
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (JSONException e) {
                    e.printStackTrace();
                } finally {
                    if (urlConnection != null) {
                        urlConnection.disconnect();
                    }
                    if (reader != null) {
                        try {
                            reader.close();
                        } catch (final IOException e) {
                            Log.e("MainActivity", "Error closing stream", e);
                        }
                    }
                }
                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                matchAdapter.notifyDataSetChanged();
            }
        }

        public void refreshFragment(String apiLinks, int apiType){
            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            MatchesFragment fragment = new MatchesFragment();
            Bundle args = new Bundle();
            args.putString("ApiLink", apiLinks);
            args.putString("apiType", String.valueOf(apiType));
            fragment.setArguments(args);
            fragmentTransaction.replace(R.id.linearfr, fragment);
            fragmentTransaction.commit();
        }

    }

Answer 1

THere are a few things to consider when working with a spinner. It always has a selected value and the default value selected is the first one. Therefore, when the fragment is created the first value in the spinner is selected.

When you manually open the dropdown and select the first item for the first time, it is currently selected by default and therefore your selection is not triggered and thus refresh is not called. The trick is to add dummy item as the first one and ignore position 0 in onClick (which you're already doing).

The infinite loop is happening because spinner selects the first item by default when the view is created and therefore onClick with position 0 is triggered which calls refresh again, changes fragment, new spinner is created, first item is selected, and the vicious cycle continues.