Preference changes only happen when restarting the app

Question

I was coding an app I added a preferences menu, and it works, but changes happen only when I restart the application,anyone knows how to make changes happen whithout exitting the app??? Thanks in advance ;)

My code ( from main activity):

preferencias = preferenceManager.getDefaultSharedPreferences(TimeToSpeechActivity.this);

OnSharedPreferenceChangeListener listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
      public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
       //nothing here, do I have to put anything?
      }
    };
preferencias.registerOnSharedPreferenceChangeListener(listener);

getPrefs();
changefont(fuente, letra);
if (boole == true) {fontcolors();}

private void getPrefs(){
      fuente = Typeface.createFromAsset(getAssets() , preferencias.getString("elegirfuente", "fonts/Default.ttf"));
     letra = Integer.parseInt(preferencias.getString("fontstyle", "0"));
     bol = preferencias.getBoolean("randomcolors", true);
 }

I have nothing put in preference activity, do i have to put anything?

Also, do I have to edit this?: (SharedPreferences prefs, String key) I ask this because i havent created prefs and key varibles

Thanks in advance!!! ;)

EDIT1: Added preference activity

     public class PantallaOpciones extends PreferenceActivity {

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

       addPreferencesFromResource(R.xml.opciones);
          }
        }

Answer 1

Maybe you want to use SharedPreferences like follows:

String PREFS_NAME = "com.example.sp", PREFS_TEST = "com.examples.sp.test";
SharedPreferences preferences;

preferences = getSharedPreferences(PREFS_NAME,MODE_PRIVATE);
// This is how you instantiate a SharedPreference object.

preferences.edit().putString(PREFS_TEST,"TEST").commit();
// This way the preference is actually modified and saved.