App crashes when orientation changes in fragment

Question

The app crashes when changing the orientation. It show a NullPointerException. I believe that it has something to do with the way SharedPreferences are stored in saveInSp() method. But can't narrow down on the issue. The test() method is being called in onAttach(). The context should have been available then?

Error:

2019-10-28 07:50:30.081 19188-19188/com.example E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example, PID: 19188
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences androidx.fragment.app.FragmentActivity.getSharedPreferences(java.lang.String, int)' on a null object reference
    at com.example.OneFragment.saveInSp(OneFragment.java:730)
    at com.example.OneFragment.access$600(OneFragment.java:52)
    at com.example.OneFragment$14.onResponse(OneFragment.java:664)
    at com.example.OneFragment$14.onResponse(OneFragment.java:654)

Fragment Code:

public class OneFragment extends Fragment implements
        OnChartValueSelectedListener {
    private OnFragmentInteractionListener listener;
    public static OneFragment newInstance() {
        return new OneFragment();
    }
    View rootView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        rootView = inflater.inflate(R.layout.fragment_one, container, false);
        return rootView;

    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            listener = (OnFragmentInteractionListener) context;
            test();//Calling test()
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        listener = null;
    }

    public interface OnFragmentInteractionListener {
    }


    private void test(){
        String tokenUrl = "http://test.org/123/tokener";

        StringRequest request = new StringRequest(Request.Method.POST, tokenUrl, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                if (!response.equals(null)) {

                    try {
                        //Do it with this it will work
                        JSONObject auth = new JSONObject(response);
                        String at = auth.getString("token");
                        String atType = auth.getString("type");
                        saveInSp("access", at);
                        WEB_CALL();
                    } catch (JSONException e) {
                        e.printStackTrace();
                        //.makeText(getApplicationContext(), "Error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                    }
                    Log.e("Your Array Response", response);
                } else {
                    Log.e("Your Array Response", "Data Null");
                }
            }

        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e("error is ", "" + error);
            }
        }) {

        };

        if (requestQueue2 == null) {
            requestQueue2 = Volley.newRequestQueue(getActivity());
            requestQueue2.add(request);
        } else {
            requestQueue2.add(request);
        }
    }

    private String getFromSP(String key) {
        SharedPreferences preferences = getActivity().getSharedPreferences("PROJECT_NAME", android.content.Context.MODE_PRIVATE);
        return preferences.getString(key, "");
    }

    private void saveInSp(String key, String value) {
        SharedPreferences preferences = getActivity().getSharedPreferences("PROJECT_NAME", android.content.Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = preferences.edit();
        editor.putString(key, value);
        editor.apply();
    }

}

Answer 1

When a config gets changed it recreates the whole activity. In your case you send a request to the network and try to save something. Since it's initialized in a callback function this might be the issue.

Try this:

• Define a field in your Fragment class as a sharedPreference instance:

SharedPreferences preference;

• In your onCreateView initialize it with your context with checking the nullability:

if (getContext() != null) {
   preference = getContext().getSharedPreferences("PROJECT_NAME", android.content.Context.MODE_PRIVATE);
}

• And use this object to interact with sharedPreferences:

private void saveInSp(String key, String value) {
        if (preferences != null) {
             // Something was wrong. It's null
             return;
        }
        SharedPreferences.Editor editor = preferences.edit();
        editor.putString(key, value);
        editor.apply();
}

Let me know if it was helpful.