Access array values from another class

Question

I hope the following makes sense...

I have class A which does the below:

Class A

public class a extends fragment {

    private List<AllUserAdoptIdsData> dataListAdoptIds;

        public View onCreateView(.... {

          dataListAdoptIds = new ArrayList<>();

          populateAdoptIdsData("a");
       }

public void populateAdoptIdsData(final String email) {

    dataListAdoptIds.clear();

    AsyncTask<Object,Void,Void> task = new AsyncTask<Object, Void, Void>() {

        @Override
        protected Void doInBackground(Object... params) {

            String email = (String)params[0];

            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url("http://localhost/app_scripts/getUserAdoptPostIds2.php?email="+email )
                    .build();
            try {
                Response response = client.newCall(request).execute();

                JSONArray array = new JSONArray(response.body().string());

                for (int i=0; i<array.length(); i++){

                    JSONObject object = array.getJSONObject(i);

                    AllUserAdoptIdsData data = new AllUserAdoptIdsData(
                            object.getInt("ADOPT_ID")
                    );
                    dataListAdoptIds.add(data);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                System.out.println("End of content"+e);
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            adapter.notifyDataSetChanged();
        }
    };
    task.execute(email);
  }
}

AllUserAdoptIdsData

package com.example.admin.paws;

import android.util.Log;

import java.util.ArrayList;
import java.util.List;

public class AllUserAdoptIdsData {
    public int adopt_id;
    private List<Integer> list;

    public AllUserAdoptIdsData(int adopt_id)
    {
     list = new ArrayList<Integer>();
     list.add(adopt_id);
     this.adopt_id = adopt_id;

        Log.d("LOG", "AllUserAdoptIdsData: "+list.size());
    }

    public int getId() {
        return adopt_id;
    }

    public List<Integer> getList() {
        return list;
    }

}

Now I have class B in which I want to get the values added to AllUserAdoptIdsData in class A. As you can see I tried to follow this link (Java - How to access an ArrayList of another class?), but obviously every time AllUserAdoptIdsData is initiated it creates a new array. Not sure where I'm going wrong.

Class B

public class B extends Fragment {

   public View onCreateView(....{

   //Here I'm trying to see if the list contains a specific value.

        AllUserAdoptIdsData allUserAdoptIdsData;
        allUserAdoptIdsData = new AllUserAdoptIdsData(0);

        List<Integer> list = allUserAdoptIdsData.getList();
        Log.d("LOG", "lookupAdoptId: "+list.contains(209));
   }

Store your values, in saveInstanceState or other appropriate mechanism. — Prashant Abdare, Apr 20 '18 at 10:06

score 0 · Answer 1 · answered Apr 20 '18 at 10:13

...but obviously every time AllUserAdoptIdsData is initiated it creates a new array.

that's because you instantiate it every time when you call

AllUserAdoptIdsData allUserAdoptIdsData;
allUserAdoptIdsData = new AllUserAdoptIdsData(0);

To access the contents of the array(list) from a different class (especially different Fragments) you need to think of a way to provide this data between different Activities/Fragments (see this answer).

Also don't confuse Array and (Array)List!

score 0 · Answer 2 · answered Apr 20 '18 at 10:56

See you have created a custom list using Model class.Please understand following point

In java constructor is use for initialise objects - you are initialising the int values through constructor of Model class to 0 every time.
There is a access specifier of an object which define their accessibility of specific object - you want to access list data from fragment a to fragment b so you need to declare public access specifier to list.
Once you have initialise any object to a specific values then previously initialised values get overwrite - in your Fragment b you are initialising your object to new object with some values every time it get initialised.

Access array values from another class

2 Answers2