onSharedPreferenceChanged not fired if change occurs in separate activity?

Question

I've implemented onSharedPreferenceChanged in my main activity.

If I change the preferences in the main activity, my event fires.

If I change the preferences through my preferences screen (PreferenceActivity) my event does NOT fire when preferences are changed (because it's a separate activity and separate reference to sharedPreferences?)

Does anybody have a recommendation of how I should go about overcoming this situation?

Thanks!

EDIT1: I tried adding the event handler right in my preference activity but it never fires. The following method gets called during onCreate of my preference activity. When I change values, it never prints the message (msg() is a wrapper for Log.d).

private void registerChangeListener () {
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this);

    sp.registerOnSharedPreferenceChangeListener(new OnSharedPreferenceChangeListener () {
        public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
            msg (" ***** Shared Preference Update ***** ");
            Intent i = new Intent();
            i.putExtra("KEY", key);
            i.setAction("com.gtosoft.dash.settingschanged");

            sendBroadcast(i);

            // TODO: fire off the event
        }
    });
}

Answer 1

The OnSharedPreferenceChangeListener gets garbage collected in your case if you use an anonymous class.

To solve that problem use the following code in PreferenceActivity to register and unregister a change listener:

public class MyActivity extends PreferenceActivity implements
    OnSharedPreferenceChangeListener {

@Override
protected void onResume() {
    super.onResume();
    // Set up a listener whenever a key changes
    getPreferenceScreen().getSharedPreferences()
            .registerOnSharedPreferenceChangeListener(this);
}

@Override
protected void onPause() {
    super.onPause();
    // Unregister the listener whenever a key changes
    getPreferenceScreen().getSharedPreferences()
            .unregisterOnSharedPreferenceChangeListener(this);
}

public void onSharedPreferenceChanged(SharedPreferences sharedPreferences,String key) 
{
  // do stuff
}

Furthermore be aware that the listener only gets called if the actual value changes. Setting the same value again will not fire the listener.

see also SharedPreferences.onSharedPreferenceChangeListener not being called consistently

Answer 2

This happen because garbage collector. its works only one time. then the reference is collected as garbage. so create instance field for listener.

private OnSharedPreferenceChangeListener listner;

listner = new SharedPreferences.OnSharedPreferenceChangeListener() {        
        @Override
        public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
            //implementation goes here
        }
    };
    prefs.registerOnSharedPreferenceChangeListener(listner);

Answer 3

I arrived here, like many others, because my listener won't be fired when I changed my boolean from true to false, or viceversa.

After much reading, and refactoring, switching contexts/inner classes/privates/static/ and the like, I realized my (stupid) error:

The onSharedPreferenceChanged is only called if something changes. Only. Ever.

During my tests, I was so dumb to click on the same button all the time, thus assigning the same boolean value to the preference all the time, so it did not ever change.

Hope this helps somebody!!