聆听偏好变更

Question

In my Main activity I would like to listen to changes made in the Preferences Activity. I use

    SharedPreferences prefs =
            PreferenceManager.getDefaultSharedPreferences(getBaseContext());
    SharedPreferences.OnSharedPreferenceChangeListener listener =
            new SharedPreferences.OnSharedPreferenceChangeListener() {
        public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
            //implement here -> but this peace of code is never called
        }
    };
    prefs.registerOnSharedPreferenceChangeListener(listener);

But the listener is never called. In my SettingsActivity I use the generated code from the Android Studio Template. For instance

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class GeneralPreferenceFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_general);
        setHasOptionsMenu(true);
        bindPreferenceSummaryToValue(findPreference("my_list"));
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            startActivity(new Intent(getActivity(), SettingsActivity.class));
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

How to fix this?

Answer 1

You need to hold onto a reference of your listener in your SettingsActivity. SharedPreferences only holds onto a Weak Reference, which means your listener doesn't get called.