Как сделать так, чтобы при использовании viewpager floating action button оставалась на месте, но менялась иконка и функционал?

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    }

@Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_message, container, false);

        Toolbar toolbar = view.findViewById(R.id.toolbar);
        ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
        toolbar.setTitle(getString(R.string.message_fragment));

        viewPager = (ViewPager) view.findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabs = (TabLayout) view.findViewById(R.id.tablayout);
        tabs.setupWithViewPager(viewPager);

        return view;
    }

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager());
        adapter.addFrag(new Messages_Tabs_ChatFragment(), "Чаты");
        adapter.addFrag(new Messages_Tabs_CallFragment(), "Звонки");
        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);
        }
    }