Comment charger un fragment de données lorsqu'il est visible par l'utilisateur et conserver les données après le chargement

Question

J'ai utilisé la méthode setUserVisibleHint() pour charger des données, mais cette méthode a été appelée avant oncreateview, donc j'obtiens NPE.

J'ai vérifié avec les soloutions sur le débordement de pile des liens mentionnés ci-dessous.

setUserVisibleHint called before onCreateView in Fragment

setUserVisibleHint with Fragments for android

Je veux charger des données lorsque fragment est visible à l'utilisateur et je veux conserver les données qu'il est après once.It chargement ne devrait pas clair après avoir glissé au fragment suivant.

S'il vous plaît aidez-moi avec ceci. J'ai totalement 5 fragments. Dans chaque fragment je fais appel au serveur dans la méthode onCreateView du fragment. Voici l'exemple d'un fragment.

package com.geelani.sestoauto.list; 


import android.app.Dialog; 
import android.content.Context; 
import android.content.SharedPreferences; 
import android.os.Bundle; 
import android.preference.PreferenceManager; 
import android.support.design.widget.FloatingActionButton; 
import android.support.v4.app.Fragment; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.ImageView; 
import android.widget.ListView; 
import android.widget.ProgressBar; 
import android.widget.Toast; 

import com.example.taha.myapplication.backend.model.pricesApi.model.Prices; 
import com.example.taha.myapplication.backend.model.specsPricesApi.SpecsPricesApi; 
import com.example.taha.myapplication.backend.model.specsPricesApi.model.CollectionResponseSpecsPrices; 
import com.example.taha.myapplication.backend.model.specsPricesApi.model.SpecsPrices; 
import com.geelani.sestoauto.MainActivity; 
import com.geelani.sestoauto.R; 
import com.geelani.sestoauto.async.GenericAsyncTaskList; 
import com.geelani.sestoauto.async.ResponseListener; 
import com.geelani.sestoauto.utils.Constants; 
import com.google.api.client.extensions.android.http.AndroidHttp; 
import com.google.api.client.json.gson.GsonFactory; 

import java.util.ArrayList; 
import java.util.HashMap; 


/** 
* A simple {@link Fragment} subclass that shows a list of featured lists a user can see. 
* Use the {@link SpecsFragment#newInstance} factory method to 
* create an instance of this fragment. 
*/ 
public class SpecsFragment extends Fragment implements ResponseListener { 

    private String title; 
    private String location; 
    private ProgressBar mProgBar; 
    private SpecsAdapter mAdapter; 
    private CollectionResponseSpecsPrices specs; 
    private ArrayList<SpecsPrices> items = new ArrayList(); 
    private ArrayList<Prices> items1 = new ArrayList(); 
    private Context mContext; 
    private ImageView handler; 
    ListView listView; 
    SharedPreferences getPrefs; 
    private boolean isViewShown = false; 


    public SpecsFragment() { 
     /* Required empty public constructor */ 
    } 


    /** 
    * Create fragment and pass bundle with data as it's arguments 
    */ 
    public static SpecsFragment newInstance(String title, String location) { 
     SpecsFragment fragment = new SpecsFragment(); 
     Bundle args = new Bundle(); 
     args.putString(Constants.TITLES, title); 
     args.putString(Constants.LOCATION, location); 
     fragment.setArguments(args); 
     return fragment; 
    } 

    @Override 
    public void setUserVisibleHint(boolean isVisibleToUser) { 
     super.setUserVisibleHint(isVisibleToUser); 
     if (getView() != null) { 
      isViewShown = true; 
      // fetchdata() contains logic to show data when page is selected mostly asynctask to fill the data 
      listSpecs(); 
     } else { 
      isViewShown = false; 
     } 
    } 

    /** 
    * Initialize instance variables with data from bundle 
    */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     if (getArguments() != null) { 
      title = getArguments().getString(Constants.TITLES); 
      location = getArguments().getString(Constants.LOCATION); 
      //  Log.d("location",location.toString()); 
      if (!isViewShown) { 
       listSpecs(); 
      } 

     } 

    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     mContext = getContext(); 
     View mView = inflater.inflate(R.layout.fragment_specifications, container, false); 
     getPrefs = PreferenceManager 
       .getDefaultSharedPreferences(mContext); 
     if (getPrefs.getString(Constants.CITY, null) == null) { 

      searchCitiesList(); 

     } 
     RecyclerView mRecy = (RecyclerView) mView.findViewById(R.id.rv_ff); 
     mProgBar = (ProgressBar) mView.findViewById(R.id.prog_bar_ff); 
     handler = (ImageView) mView.findViewById(R.id.handler); 
     mRecy.setLayoutManager(new LinearLayoutManager(getContext())); 


     mAdapter = new SpecsAdapter(mContext); 
     mRecy.setAdapter(mAdapter); 
     listSpecs(); 
     return mView; 
    } 

    private void listSpecs() { 

     mProgBar.setVisibility(View.VISIBLE); 
     SpecsPrices specs = new SpecsPrices(); 
     SpecsPricesApi api = new 
       SpecsPricesApi(AndroidHttp.newCompatibleTransport(), new GsonFactory(), null 
     ); 
     GenericAsyncTaskList<SpecsPricesApi, SpecsPrices, SpecsFragment> asyncTask = new GenericAsyncTaskList<SpecsPricesApi, SpecsPrices, SpecsFragment>(
       api, 
       specs, 
       this, 
       getActivity(), 
       null, 
       title, 
       "make", 
       "basemodel", 
       "Mumbai", 
       Constants.LIST_SPECSPRICES, 
       "false" 
     ); 
     asyncTask.execute(); 

    } 


    public void searchCitiesList() { 
     final Dialog dialog = new Dialog(mContext); 
     dialog.setContentView(R.layout.select_city); 
     dialog.setTitle("Select City"); 
     listView = (ListView) dialog.findViewById(R.id.list1); 

     String[] values = new String[]{"Mumbai", "New Delhi", "Bangalore", "Pune", "Chennai", "Kolkata", "Hyderabad", "Ahmedabad", "Chandigarh", "Gurgaon" 
       , "Noida", "Navi-Mumbai", "Thane", "Cochin", "Faridabad", "Ghaziabad"}; 
     dialog.show(); 
     ArrayAdapter<String> adapter = new ArrayAdapter<String>(mContext, 
       R.layout.listcity, R.id.city1, values); 
     listView.setAdapter(adapter); 
     listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 

      @Override 
      public void onItemClick(AdapterView<?> parent, View view, 
            int position, long id) { 
       int itemPosition = position; 
       String itemValue = (String) listView 
         .getItemAtPosition(position); 
       SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(mContext); 
       SharedPreferences.Editor editor = settings.edit(); 
       editor.putString(Constants.CITY, itemValue); 
       editor.commit(); 
       // Show Alert 
       Toast.makeText(
         mContext, 
         "selected" + itemValue, Toast.LENGTH_LONG).show(); 
       dialog.cancel(); 

      } 

     }); 
    } 

    /** 
    * Updates the order of mListView onResume to handle sortOrderChanges properly 
    */ 
    @Override 
    public void onResume() { 
     super.onResume(); 


    } 

    /** 
    * Cleanup the adapter when activity is paused. 
    */ 
    @Override 
    public void onPause() { 
     super.onPause(); 
    } 


    @Override 
    public void processlistener(String type, Object result) { 
     if (type.contentEquals(Constants.LIST_SPECSPRICES)) { 
      specs = (CollectionResponseSpecsPrices) result; 
      items = (ArrayList<SpecsPrices>) specs.getItems(); 
      mProgBar.setVisibility(View.GONE); 
      mAdapter.addItems(items, items1, title); 
      //listprices(); 
     } else { 
      handler.setVisibility(View.VISIBLE); 
      mProgBar.setVisibility(View.GONE); 

     } 
    } 
} 

Answer 1

essayer avec ceci:

private boolean _hasLoadedOnce = false; // your boolean field 

    @Override 
    public void setUserVisibleHint(boolean isFragmentVisible_) { 
     super.setUserVisibleHint(true); 

     if (this.isVisible()) { 
      // we check that the fragment is becoming visible 
      if (isFragmentVisible_ && !_hasLoadedOnce) { 
       if (global.isNetworkAvailable()) { 

        listSpecs(); 

       } 
       _hasLoadedOnce = true; 
      } 
     } 
    }