protected void onCreate(Bundle savedInstanceState) {
 PreferenceManager.getDefaultSharedPreferences(getApplicationContext())
  .registerOnSharedPreferenceChangeListener(new OnSharedPreferenceChangeListener() {
  @Override
  public void onSharedPreferenceChanged(
   SharedPreferences sharedPreferences, String key) {
   Log.i(LOGTAG, "testOnSharedPreferenceChangedWrong key =" + key);
  }
 });
}

private final WeakHashMap<OnSharedPreferenceChangeListener, Object> mListeners =
   new WeakHashMap<OnSharedPreferenceChangeListener, Object>();
//some code goes here
public void More ...registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener) {
 synchronized(this) {
  mListeners.put(listener, mContent);
 }
}

private OnSharedPreferenceChangeListener mListener = new OnSharedPreferenceChangeListener() {

 @Override
 public void onSharedPreferenceChanged(
  SharedPreferences sharedPreferences, String key) {
  Log.i(LOGTAG, "instance variable key=" + key);
 }
};

@Override
protected void onResume() {
 PreferenceManager.getDefaultSharedPreferences(getApplicationContext()).registerOnSharedPreferenceChangeListener(mListener);
 super.onResume();
}

@Override
protected void onPause() {
 PreferenceManager.getDefaultSharedPreferences(getApplicationContext()).unregisterOnSharedPreferenceChangeListener(mListener);
 super.onPause();
}

private static OnSharedPreferenceChangeListener sListener = new OnSharedPreferenceChangeListener() {
 @Override
 public void onSharedPreferenceChanged(
  SharedPreferences sharedPreferences, String key) {
  Log.i(LOGTAG, "static variable key=" + key);
 }
};