How to initialize the components of a layout in the onCreate of a Fragment?

Question

I created a Fragment to show a list of items, but I need to initialize two components a listview and a Progressbar on onCreate but I don’t have the reference of the layout file they are. How do I boot them into onCreate? Below follows the code.

public class HerosFragment extends Fragment {

    private static final int CODE_GET_REQUEST = 1024;
    private static final int CODE_POST_REQUEST = 1025;

    //Variaveis dos componentes
    EditText editTextHeroId, editTextName, editTextRealname;
    RatingBar ratingBar;
    Spinner spinnerTeam;
    ProgressBar progressBarList;
    ListView listView;

    FloatingActionButton fabAddHero;

    //vamos usar essa lista para exibir herói na lista
    List<Hero> heroList;

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

        //Preciso inicializar esses dois componentes mas não consigo
        progressBarList = (ProgressBar) findViewById(R.id.progressBarList);
        listView = (ListView) findViewById(R.id.listViewHeroes);

        heroList = new ArrayList<>();
        readHeroes();
    }

    //Recupera os dados dos herois do banco de dados
    private void readHeroes() {
        PerformNetworkRequest request = new PerformNetworkRequest(Api.URL_READ_HEROES, null, CODE_GET_REQUEST);
        request.execute();
    }

    //Para atualizar a lista de herois
    private void refreshHeroList(JSONArray heroes) throws JSONException {
        //limpa herois anteriores
        heroList.clear();

        //Cria uma nova lista com os herois atualizados do JSON de resposta
        for (int i = 0; i < heroes.length(); i++) {
            //getting each hero object
            JSONObject obj = heroes.getJSONObject(i);

            //adiciona os herois a lista
            heroList.add(new Hero(
                    obj.getInt("id"),
                    obj.getString("name"),
                    obj.getString("realname"),
                    obj.getInt("rating"),
                    obj.getString("teamaffiliation")
            ));
        }

        //cria um adapter com a lista de herois
        CustomAdapterHero adapter = new CustomAdapterHero(this.getActivity(), heroList);
        listView.setAdapter(adapter);
    }

    //classe interna para executar solicitação de rede estendendo um AsyncTask
    private class PerformNetworkRequest extends AsyncTask<Void, Void, String> {

        //o URL onde precisa enviar a solicitação
        String url;

        //Os parametros
        HashMap<String, String> params;

        //O código do pedido para definir se é um GET ou POST
        int requestCode;

        //Construtor para inicializar os valores
        PerformNetworkRequest(String url, HashMap<String, String> params, int requestCode) {
            this.url = url;
            this.params = params;
            this.requestCode = requestCode;
        }

        //Quando a tarefa começou a exibir uma barra de progresso
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressBarList.setVisibility(View.VISIBLE);
        }

        //Este método dará a resposta do pedido
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            progressBarList.setVisibility(GONE);
            try {
                JSONObject object = new JSONObject(s);
                if (!object.getBoolean("error")) {
                    //atualizando o herolista após cada operação
                    //então nós conseguimos uma lista atualizada
                    refreshHeroList(object.getJSONArray("heroes"));
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }

        //A operação da rede será realizada em segundo plano
        @Override
        protected String doInBackground(Void... voids) {
            RequestHandler requestHandler = new RequestHandler();

            if (requestCode == CODE_POST_REQUEST)
                return requestHandler.sendPostRequest(url, params);


            if (requestCode == CODE_GET_REQUEST)
                return requestHandler.sendGetRequest(url);

            return null;
        }
    }

}

Answer 1

You need to inflate the fragment layout in the method onCreateView. Example:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_heroes, container, false);
    progressBarList = (ProgressBar) rootView.findViewById(R.id.progressBarList);
    listView = (ListView) rootView.findViewById(R.id.listViewHeroes);
    return rootView;

}

Substitute fragment_heroes by name of the layout of your Fragment.

The other actions you’re doing on onCreate, you’ll probably have to do them on onResume, or in the onViewCreated.