如何以相同的方法返回片段和片段活动？

Question

我有三个标签。其中两个扩展Fragment，第三个标签扩展FragmentActivity。 getItem()方法如何实现？

public class UpdatesFragment extends FragmentActivity  {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.updates_layout);

        if (savedInstanceState == null) {
            addRssFragment();
        }
    }

    private void addRssFragment() {
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        RssFragment fragment = new RssFragment();
        transaction.add(R.id.fragment_container, fragment);
        transaction.commit();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putBoolean("fragment_added", true);
    }
}

public class TabFragment extends Fragment {

    public static TabLayout tabLayout;
    public static ViewPager viewPager;
    public static int int_items = 3;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         /**
         *Inflate tab_layout and setup Views.
         */
        View x =  inflater.inflate(R.layout.tab_layout,null);
        tabLayout = (TabLayout) x.findViewById(R.id.tabs);
        viewPager = (ViewPager) x.findViewById(R.id.viewpager);

        /**
         *Set an Apater for the View Pager
         */
        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));

        /**
         * Now , this is a workaround ,
         * The setupWithViewPager dose't works without the runnable .
         * Maybe a Support Library Bug .
         */

        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                    tabLayout.setupWithViewPager(viewPager);
            }
        });

        return x;
    }
}

class MyAdapter extends FragmentPagerAdapter{

    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    /**
     * Return fragment with respect to Position .
     */
    @Override
    public Fragment getItem(int position)
    {
      switch (position){
          case 0 : return new PrimaryFragment();
          case 1 : return new SocialFragment();
          case 2:  return new UpdatesFragment();
      }

    return null;
    }

    @Override
    public int getCount() {
        return int_items;
    }

    /**
     * This method returns the title of the tab according to the position.
     */

    @Override
    public CharSequence getPageTitle(int position) {

        switch (position){
            case 0 :
                return "Primary";
            case 1 :
                return "Social";
            case 2 :
                return "Updates";
        }
            return null;
    }
}

Answer 1

Fragment 和 FragmentActivity 都是不同的东西。我们可以在FragmentActivity 中包含Fragment。但是您不能将FragmentActivity 用作Fragment。如果你想在你的ViewPager 中使用UpdatesFragment，那么从Fragment 扩展它。