Question

此代码正常运行，但当我跳转到另一个片段时，正在执行几次次。

例如，这是第一个片段，如果我转到第三个（或者例如第四个“差异多个片段”）并返回到首先，它将再次执行onCreateView（）。

我知道这是正常的，我想我想将它更改为onCreate（）方法，但在我的情况下，我想我会得到空值，因为还没有任何UI（例如获取微调器）。

想法是从php webservice 填充微调器。

有什么想法解决这个问题吗？谢谢你的帮助。

   public class ProfessoresFragment extends Fragment {

    private Spinner spinnerProfessores;

    // array list for spinner adapter
    private ArrayList<Teacher> TeacherList;
    ProgressDialog pDialog;

    // API urls
    // Url to get all teachers
    private String URL_TEACHERS = "http://10.0.2.2/android/GetAllTeachersJson.php";

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

        View rootView = inflater.inflate(R.layout.fragment_professores, container, false);

        spinnerProfessores = (Spinner) rootView.findViewById(R.id.spinner);                 
        TeacherList = new ArrayList<Teacher>(); 
        new GetTeachers().execute();    
        return rootView;
    }

    /**
     * Adding spinner data
     * */

    private void populateSpinner() {
        List<String> lables = new ArrayList<String>();

        for (int i = 0; i < TeacherList.size(); i++) {
            lables.add(TeacherList.get(i).getProfessor());
        }

        // Creating adapter for spinner
        ArrayAdapter<String> spinnerAdapter = new ArrayAdapter<String>(getActivity(),
        android.R.layout.simple_spinner_item, lables);

        // Drop down layout style - list view with radio button
        spinnerAdapter
                .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // attaching data adapter to spinner
        spinnerProfessores.setAdapter(spinnerAdapter);
    }


       private class GetTeachers extends AsyncTask<Void, Void, Void> {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                pDialog = new ProgressDialog(getActivity());
                pDialog.setMessage("A processar professores..");
                pDialog.setCancelable(false);
                pDialog.show();

            }

            @Override
            protected Void doInBackground(Void... arg0) {
                ServiceHandler jsonParser = new ServiceHandler();
                String json = jsonParser.makeServiceCall(URL_TEACHERS, ServiceHandler.GET);

                Log.e("Response: ", "> " + json);

                if (json != null) {
                    try {
                        JSONObject jsonObj = new JSONObject(json);
                        if (jsonObj != null) {
                            JSONArray teachers = jsonObj
                                    .getJSONArray("professores");                        

                            for (int i = 0; i < teachers.length(); i++) {
                                JSONObject TeaObj = (JSONObject) teachers.get(i);
                                Teacher Tea = new Teacher(TeaObj.getInt("Cod_Professor"),
                                        TeaObj.getString("Professor"));
                                TeacherList.add(Tea);
                            }
                        }

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

                } else {
                    Log.e("JSON Data", "Didn't receive any data from server!");
                }

                return null;
            }

            @Override
            protected void onPostExecute(Void result) {
                super.onPostExecute(result);
                if (pDialog.isShowing())
                    pDialog.dismiss();
                populateSpinner();
            } 
        }
}

Answer 1

当您离开Fragment时，请将其删除，以便下次访问时使用FragmentMananger和Transaction

来调用onCreate

多次调用onCreateView（） - 更改为onCreate（）

1 个答案: