public Item(@NonNull Preference preference, @NonNull Setter setter, @NonNull CfgBase cfg) {
   this.preference = preference;
   this.setter = setter;
   this.cfg = cfg;
   this.option = cfg.getOption(preference.getKey());
 }
 /**
  * Stops to listen to the changes.
  *
  * @see #start()
  */
 public void stop() {
   mStarted = false;
   mCfg.unregisterListener(mConfigListener);
   for (Item item : mItems) item.preference.setOnPreferenceChangeListener(null);
 }