Why does my TaskLoader only stores the last data?

Question

I am having problem with the flow of my code. Please please please help :(

Okay, so the flow goes like this. the first Activity loads the recyclerviewwhich stores the ArrayListdata. The data of the Arraylist consist of information about a Premise which it retrieve from an API of a website. It uses GET method.

Okay, next when I select an item from the recyclerview, it brings me to the next Activity which I will enter an integer. Then, as it returns to the first Activity, it passes the integer value and the index of the recyclerview item. The recyclerview updates the item with the index and stores the integer value in the item.

So, my problem is: when I repeat the process of selecting an item from the recyclerview and enter an integer, the first activity only stores the latest data. the previous item is gone.

Where on Earth did I did wrong? I am new to mobile app development. Please help. I am beyond clueless.

Here's the first Activity. It's called MainActivity:

public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<ArrayList<Premise>> {

    private NotificationManagerCompat notificationManager;

    private LoaderManager loaderManager;
    private RecyclerView rcvPremises;
    private EditText premiseSearch;

    String pTrackVisitor_s, pPosition_s, pPremiseName, pLocation;
    int pTrackVisitor, pPosition;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        loaderManager = LoaderManager.getInstance(this);
        premiseSearch = findViewById(R.id.search);
        rcvPremises = findViewById(R.id.rcvPremise);

        Intent mainIntent = getIntent();
        pTrackVisitor_s = mainIntent.getStringExtra("trackVisitor");
        pPosition_s = mainIntent.getStringExtra("position");

        if (pTrackVisitor_s != null) {
            pTrackVisitor = Integer.parseInt(pTrackVisitor_s);
            pPosition = Integer.parseInt(pPosition_s);
        } else {
                pTrackVisitor = 0;
                pPosition = 0;
        }
    }

    @NonNull
    @Override
    public Loader<ArrayList<Premise>> onCreateLoader(int id, @Nullable Bundle args) {
        return new PremisesListTaskLoader(this, pTrackVisitor, pPosition);
    }

    @Override
    public void onLoadFinished(@NonNull Loader<ArrayList<Premise>> loader, ArrayList<Premise> vPremise) {
        loaderManager.destroyLoader(0);

        if (!vPremise.isEmpty()) {

            rcvPremises.setAdapter(new PremiseAdapter(this, vPremise));
            rcvPremises.setLayoutManager(new LinearLayoutManager(this));
            premiseSearchBar(premiseSearch, vPremise);
        } else
            Toast.makeText(this, "Unable to load data from iiotisme.com", Toast.LENGTH_LONG).show();
    }

    @Override
    public void onLoaderReset(@NonNull Loader<ArrayList<Premise>> loader) {
    }
}

Please let me know if you need more parts of the coding. I 'll share them.

Answer 1

First of all, you should not read data in onCreate, it will be only triggered when Activity is created first time, I assume your activity will be resume, it should use something like onActivityResult. You should start second activity using startActivityForResult and in onActivityResult, you will get an intent from where you can read the latest data every time.

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(data == null) 
            return;
        pTrackVisitor_s = data.getStringExtra("trackVisitor");
        pPosition_s = data.getStringExtra("position");

        if (pTrackVisitor_s != null) {
            pTrackVisitor = Integer.parseInt(pTrackVisitor_s);
            pPosition = Integer.parseInt(pPosition_s);
        } else {
            pTrackVisitor = 0;
            pPosition = 0;
        }
    }

You can pass the index and other required data to your second activity using intent like below

Intent data = new Intent();
data.putExtra("position", <yourClickedIndex>);
startActivityForResult(1234, SecondActivity.class);