/*
  * Save the access token and expiry date so you don't have to fetch it each
  * time
  */
 public static boolean save(Facebook session, Context context) {
   Editor editor = Preferences.getSharedPreferences(KEY).edit();
   editor.putString(TOKEN, session.getAccessToken());
   editor.putLong(EXPIRES, session.getAccessExpires());
   editor.putLong(LAST_UPDATE, session.getLastAccessUpdate());
   return editor.commit();
 }
 /*
  * Restore the access token and the expiry date from the shared preferences.
  */
 public static boolean restore(Facebook session, Context context) {
   SharedPreferences savedSession = Preferences.getSharedPreferences(KEY);
   session.setTokenFromCache(
       savedSession.getString(TOKEN, null),
       savedSession.getLong(EXPIRES, 0),
       savedSession.getLong(LAST_UPDATE, 0));
   return session.isSessionValid();
 }
 /**
  * clears facebook login credentials from the preferences
  *
  * @param context
  */
 public static void clear(Context context) {
   Editor editor = Preferences.getSharedPreferences(KEY).edit();
   editor.clear();
   editor.commit();
 }