Array of custom object model won't save to shared preferences

Question

I am trying to do a module where once I fetched the JSON from the API and I am loading it into RAM memory I immediately load it to Shared Prefs and also once I any change to the data (in the adapter onClick method) I re-save the new changed array into the shared preferences. Apparently it does not work and I can't figure out why.

Here is my activity containing all of the relevant code:


package com.example.superheros.Controllers;

import android.content.SharedPreferences;
import android.support.design.widget.CollapsingToolbarLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.widget.ImageView;

import com.example.superheros.Adapter.HeroesAdapter;
import com.example.superheros.Model.Hero;
import com.example.superheros.Networking.HttpRequest;
import com.example.superheros.R;
import com.google.gson.Gson;
import com.squareup.picasso.Picasso;

import java.util.ArrayList;
import java.util.Arrays;

public class MainActivity extends AppCompatActivity {

    //API constant -
    private static final String BASE_URL = "https://heroapps.co.il/employee-tests/android/androidexam.json";
    public static final String SAVED_HERO_LIST = "heroesList";
    // Recyclerview variables -
    private RecyclerView heroesRecylerView;
    private ArrayList<Hero> heroesArrayList;
    private RecyclerView.LayoutManager layoutManager;
    private HeroesAdapter heroesAdapter;
    //Toolbar variables -
    private CollapsingToolbarLayout collapsingToolbarLayout;
    private ImageView toolbarImageView;
    //Persistence variables -
    private Hero selectedFavoriteHero;
    private SharedPreferences sharedPreferences;
    private Gson gson;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        try {
            heroesArrayList = loadFromLocal();
        }catch (Exception ex) {
            ex.printStackTrace();
        }
        if (heroesArrayList != null && heroesArrayList.size() > 0){
            initViews();
        } else {
            initNetworking();
        }

    }

    private void initNetworking() {
        HttpRequest httpRequest = new HttpRequest(this, BASE_URL, new HttpRequest.OnHttpCompleteListener() {
            @Override
            public void onComplete(String response) {
                dataToModel(response, false);
                initViews();
            }

            @Override
            public void onError(String error) {
                Log.d("error", error);
            }
        });
        httpRequest.request();
    }


    private void initViews() {
        heroesRecylerView = findViewById(R.id.herosRecyclerView);
        collapsingToolbarLayout = findViewById(R.id.collapsingHeroToolbarLayout);
        toolbarImageView = findViewById(R.id.toolbarImageview);
        heroesRecylerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        heroesRecylerView.setLayoutManager(layoutManager);
        heroesAdapter = new HeroesAdapter(heroesArrayList, new HeroesAdapter.OnHeroListClickListener() {
            @Override
            public void onListItemClicked(int position) {
                changeFavoriteHero(position);
            }
        });
        heroesRecylerView.setAdapter(heroesAdapter);

    }

    private void changeFavoriteHero(int position) {
        Hero pressedHeroRow = heroesArrayList.get(position);
        selectedFavoriteHero = pressedHeroRow;
        Picasso.get().load(pressedHeroRow.image)
                .fit()
                .centerCrop()
                .placeholder(R.drawable.ic_launcher_background)
                .error(R.drawable.ic_launcher_foreground)
                .into(toolbarImageView);
        collapsingToolbarLayout.setTitle(pressedHeroRow.title);
        pressedHeroRow.setFavorite(!pressedHeroRow.isFavorite());
        for (int i = 0; i < heroesArrayList.size(); i++) {
            if (i == position) continue;
            heroesArrayList.get(i).setFavorite(false);
        }
        saveToLocal(heroesArrayList);
        heroesAdapter.notifyDataSetChanged();
    }


    private ArrayList<Hero> dataToModel(String json, boolean isLocalInfo) {
        Gson gson = new Gson();
        Hero[] heroesList = gson.fromJson(json, Hero[].class);
        heroesArrayList = new ArrayList<>(Arrays.asList(heroesList));
        if (!isLocalInfo) {
            saveToLocal(heroesArrayList);
        }
        return heroesArrayList;
    }


    //Shared preferences load & save methods -

    private void saveToLocal(ArrayList<Hero> heroesArrayList) {
        sharedPreferences = getPreferences(MODE_PRIVATE);
        SharedPreferences.Editor prefsEditor = sharedPreferences.edit();
        Gson gson = new Gson();
        String heroesList = gson.toJson(heroesArrayList);
        Log.d("heroArrayList", heroesList);
        prefsEditor.putString(SAVED_HERO_LIST, heroesList);
        prefsEditor.apply();
    }

    private ArrayList<Hero> loadFromLocal(){
        sharedPreferences = getPreferences(MODE_PRIVATE);
        try {
            String fetchedHeroesJson = gson.fromJson(SAVED_HERO_LIST, String.class);
            ArrayList<Hero> heroArrayList = dataToModel(fetchedHeroesJson, true);
            return heroArrayList;
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return null;

    }
}

I hope I can be pointed about what I was missing

SharedPreference is not Memory DB. I don't fully understand what you want to do. But delete the app completely(delete the data) and then re-try, if you want to remove the data in SharedPreference. — c-an
– c-an, Commented May 29, 2019 at 8:21
tried to delete and re-install the app and did not do anything new — Alon Shlider
– Alon Shlider, Commented May 29, 2019 at 8:25
Be specific please. I'd like to help you out. But can't understand what you need. — c-an
– c-an, Commented May 29, 2019 at 8:27

Vasudev Vyas · Accepted Answer · 2019-05-29 08:37:03Z

1

try this.

 private ArrayList<Hero> loadFromLocal(){
        sharedPreferences = getPreferences(MODE_PRIVATE);
        try {
            String fetchedHeroesJson = sharedPreferences.getString(SAVED_HERO_LIST, "null");
            ArrayList<Hero> heroArrayList = dataToModel(fetchedHeroesJson, true);
            return heroArrayList;
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return null;

    }

answered May 29, 2019 at 8:37

Vasudev Vyas

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2 Comments

Alon Shlider Over a year ago

thank you very much. solved! the issue was that I trying to get the data from shared prefs using GSON, haha.

Vasudev Vyas Over a year ago

welcome, it happens.. keep coding... will get a wonderful result :)

Gianluca Musa · Accepted Answer · 2019-05-29 08:18:59Z

0

change

prefsEditor.apply();

to

prefsEditor.commit();

apply() commits its changes to the in-memory SharedPreferences immediately but starts an asynchronous commit to disk and you won't be notified of any failures. As you're accessing the same preferences object (is a singleton) you should see a consistent view at all times but not in your case you access from separate thread.

answered May 29, 2019 at 8:18

Gianluca Musa

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2 Comments

Alon Shlider Over a year ago

does not seems to have any effect on the row item I pressed. I have an imageview that should change according to if the rowitem has been pressed and it seems like it did not saved it.

Alon Shlider Over a year ago

there is though some behavior that is interesting - it loads much faster than it does when deleting the app and re-installing, does that mean that the data has been fetched but not fully? or is it because of some other reason ?

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