Ошибка при обработке нажатия Preference

public class Activity extends AppPreferenceActivity {
private PreferenceFragment preferencesFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getFragmentManager().beginTransaction()
            .replace(android.R.id.content, new ActivityFragment())
            .commit();
}
public static class Activity extends PreferenceFragment {
    Preference prefernece;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        preference = findPreference(getString(R.string.preference_key));
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.activity_preference);
preference.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
            @Override
            public boolean onPreferenceClick(Preference preference) {
                Utils.startActivity(getActivity(), SecondActivity.class);
                return false;
            }
        });
    }
}

Выдается ошибка при нажатии на preference:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.preference.Preference.setOnPreferenceClickListener(android.preference.Preference$OnPreferenceClickListener)' on a null object

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<PreferenceScreen
    android:key="@string/preference_key"
    android:layout="@layout/preference_item_normal"
    android:title="@string/preference_title" />
</PreferenceScreen>