private void showHotTopic() {
   Fragment fragment =
       SubjectListFragment_.builder()
           .userKey(MyApp.sUserObject.global_key)
           .mType(SubjectListFragment.Type.hot)
           .build();
   getSupportFragmentManager()
       .beginTransaction()
       .replace(R.id.topic_hot_container, fragment)
       .commit();
 }
    @Override
    public Fragment getItem(int position) {
      final SubjectListFragment.Type types[] =
          new SubjectListFragment.Type[] {
            SubjectListFragment.Type.follow, SubjectListFragment.Type.join
          };

      Fragment fragment =
          SubjectListFragment_.builder()
              .userKey(MyApp.sUserObject.global_key)
              .mType(types[position])
              .build();

      saveFragment(fragment);
      return fragment;
    }