SharedPreferences NullPointerException in DialogFragment

Question

I have some trouble working with SharedPreferences in DialogFragment. And I keep getting NullPointerException in line sharedPreferences = getActivity().getSharedPreferences("pref", 0);. Here is may basic code.

public class ADialogFragment extends DialogFragment implements DialogInterface.OnClickListener {
    SharedPreferences sharedPreferences;
    public ADialogFragment(int a) {
        sharedPreferences = getActivity().getSharedPreferences("pref", 0);
        if (a == 0) {
            saveToPref(0);
        } else if (a == 1) {
            saveToPref(1);
        } else saveToPref(2);
    }
    private void saveToPref(int itemInt) {
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putInt(getString(R.string.item), itemInt);
        editor.commit();
    }
    public Dialog onCreateDialog(Bundle savedInstanceState) {
    ...
    }
}

How can i fix it?

please learn fragments lifecycle ... you cennot get activity when fragment is not attached to it ... — Selvin, Oct 20 '15 at 13:54
can you post the stacktrace. it makes it easier for the rest to answer. — shreyas, Oct 20 '15 at 13:54

score 4 · Accepted Answer · answered Oct 20 '15 at 13:54

4

You are calling getActivity() too early in fragment constructor and it returns null. A fragment is only attached to an activity in onAttach() or later in the fragment lifecycle.

Move the code that needs shared preferences to a later phase in the lifecycle.

Also note that fragments should not have constructors that take arguments. Use setArguments() to pass in parameters to fragments.

answered Oct 20 '15 at 13:54

laalto

150,114
66
286
303

Thank you for the detailed and informative answer. I`ll try your advices. – Ihor Salnikov Oct 20 '15 at 14:01

score 0 · Answer 2 · answered Oct 20 '15 at 13:52

0

The method getSharedPreferences is a method of the Context object, so just calling getSharedPreferences from a Fragment will not work.

So you need to do it like below

sharedPreferences = this.getActivity().getSharedPreferences("pref", 0);

answered Oct 20 '15 at 13:52

KishuDroid

5,411
4
30
47

And it still not working. – Ihor Salnikov Oct 20 '15 at 13:56
@Selvin : May be you are over smart and i am not. – KishuDroid Oct 21 '15 at 04:38

SharedPreferences NullPointerException in DialogFragment

2 Answers2