transfer data between 2 fragments of a TabLayout Android Studio

Question

So I have an app with a TabLayout. In there, I created 2 tabs (fragments).My first fragment is OngletCours and the 2nd one OngletNotes.

I have a ListView in the first tab/fragment. I would like to transfer the Item I clicked in that ListView to the 2nd Fragment to a TextView.

I have already tried something but I get a NullPointerException at line 23:

03-06 09:38:32.874 23677-23677/com.example.dasilvadd.students E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPointerException at com.example.dasilvadd.students.OngletNotes.onCreateView(OngletNotes.java:23)

here's the code from my 1st tab OngletCours (Only the setOnItemClickListener):

    final ListView l1 = (ListView) rootView.findViewById(R.id.ListCours);

    l1.setOnItemClickListener(new AdapterView.OnItemClickListener()
    {

        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            OngletNotes fragment = ((Onglets)getActivity()).getOngletNotes ();
            if(fragment != null) {
             l1.getItemAtPosition(i);
                //Put the value
                OngletNotes onotes = new OngletNotes();
                Bundle args = new Bundle();
                args.putString("Item","l1.getItemAtPosition(i)");
                onotes.setArguments(args);
               getFragmentManager().beginTransaction().add(R.id.container, onotes).commit();
            }
                ((Onglets)getActivity()).goToFragment(1);
        }
    });  
    return rootView;
    }

Here's the code from my 2nd tab OngletNotes :

public class OngletNotes extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.ongletnotes, container, false);
    //where i want to insert the selectedItem
    TextView Cours = (TextView)rootView.findViewById(R.id.TVCours);
    //Retrieve the value
     //THE ERROR IS HERE !
   String cours = getArguments().getString("Item");
    Cours.setText(cours);
    return rootView;
}

public static OngletNotes newInstance() {
    OngletNotes fragment = new OngletNotes();

    return fragment;
}

So, I don't know how to transfer the selected Item into the 2nd tab. Do I have to create methodes in my TabbedActivity called Onglets ? Please tell me if you need the code for that class as well.

Thank you in advance.

Answer 1

I think you got a bit confused in your logic. You are checking for null and then not doing anything if the fragment is null.

You can simplify it like this: First check if fragment is null , if so create a new instance, then put the arguments outside the if/else so you make sure you get them every time. Also put your string item in a variable.

@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
    OngletNotes fragment = ((Onglets)getActivity()).getOngletNotes ();
    if(fragment == null) {
        fragment = OngletNotes.getInstance();
    }
    String item = adapterView.getItemAtPosition(i).toString();
    //Put the value
    Bundle args = new Bundle();
    args.putString("Item",item);
    fragment.setArguments(args);
    getFragmentManager().beginTransaction().add(R.id.container, fragment).commit();
}