ac_main_activity.java

public class MainActivity extends AppCompatActivity {

    public static final ArrayList<String> TABS_TITLE = new ArrayList<>();
    private static final String FRAGMENT_MAP_TITLE = "Map";
    private static final String FRAGMENT_LIST_TITLE = "List";

    /*  */
    private FragmentPoisBinding mBinding;

    /* */
    private PoisViewModel mViewModel;


    public PoisFragment() {
        TABS_TITLE.add(FRAGMENT_MAP_TITLE);
        TABS_TITLE.add(FRAGMENT_LIST_TITLE);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        AndroidInjection.inject(this);
        super.onCreate(savedInstanceState);

        mBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        mViewModel = ViewModelProviders.of(this).get(PoisViewModel.class);
      
        initViewPager();
    }

    public PoisViewModel getViewModel() {
        return mViewModel;
    }
    
    private void initViewPager() {
        initViewPager(mBinding.viewpager);
        mBinding.tabs.setupWithViewPager(mBinding.viewpager);
    }

    private void initViewPager(ViewPager viewPager) {
        Adapter adapter = new Adapter(getSupportFragmentManager());

        PoisMapFragment poisMapFragment = new PoisMapFragment();
        poisMapFragment.setViewModel(mViewModel);

        PoisListFragment poisListFragment = new PoisListFragment();
        poisListFragment.setViewModel(mViewModel);

        adapter.addFragment(poisMapFragment, FRAGMENT_MAP_TITLE);
        adapter.addFragment(poisListFragment, FRAGMENT_LIST_TITLE);

        viewPager.setAdapter(adapter);
    }

    static class Adapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public Adapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}