How to make tabs with icons

I am trying to do an operation with tabs and pagerview I found this code on a blog, but it doesn't look like the tabs have icons instead of text ... I put the code:

ViewPagerAdapter.java

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

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

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

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

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

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

      

        
        
        
      

    

Tablayout_in_Android.java

public class Tablayout_in_Android extends Fragment {

    public Tablayout_in_Android() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_tablayout_in__android, container, false);
    }

}

      

        
        
        
      

    

OnCreate main class method

 viewPager = (ViewPager) findViewById(R.id.viewpager);
        addTabs(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.pestañas);
        tabLayout.setupWithViewPager(viewPager);

    }

    private void addTabs(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFrag(new Tablayout_in_Android(), "ONE");
        adapter.addFrag(new Tablayout_in_Android(), "TWO");
        adapter.addFrag(new Tablayout_in_Android(), "THREE");
        viewPager.setAdapter(adapter);
    }

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

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

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

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

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

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

      

        
        
        
      

    

how can i change the text for icons? Thanks to