Android Studio – How to pause a fragment in ViewPager + TabLayout when a different tab is selected?

Right now I have a tablayout with a ViewPager + adapter below it. I want to pause a fragment when a different tab is selected (not destroy/pop it, just pause it) and resume it when the fragment’s tab is selected.

public class PagerFragment extends Fragment {

    ViewPagerAdapter pagerAdapter;
    ViewPager pager;
    TabLayout tabLayout;
    int position;

    public PagerFragment() {
        super();
    }

    public void setPosition(int position) {
        this.position = position;
    }

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

    @Override
    public void onStop() {
        super.onStop();
    }

    @Override
    public void onPause() {
        super.onPause();
        pagerAdapter.clear();
        pagerAdapter.notifyDataSetChanged();
    }

    @Override
    public void onStart() {
        super.onStart();
    }

    @Override
    public void onResume() {
        super.onResume();
        if (!isAdded()) {
            pagerAdapter.instantiateItem(pager, position);
        }
    }

    @SuppressLint("InflateParams")
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ViewGroup root = (ViewGroup) inflater.inflate(R.layout.fragment_pager, null);
        pagerAdapter = new ViewPagerAdapter(getChildFragmentManager());
        setPosition(position);
        pagerAdapter.setDevicesList(devicesList);
        pager = root.findViewById(R.id.pager);
        pager.setAdapter(pagerAdapter);
       
        tabLayout = root.findViewById(R.id.tab_layout);

        for (int i = 0; i < devicesList.size(); i++) {
            tabLayout.addTab(tabLayout.newTab().setText(String.valueOf(devicesList.get(i).getName())));
        }

        TabLayout.Tab tab = tabLayout.getTabAt(position);
        if (tab != null) {
            tab.select();
            pager.setCurrentItem(position);
            tabLayout.setupWithViewPager(pager);

            tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
                @Override
                public void onTabSelected(TabLayout.Tab tab) {
                    pager.setCurrentItem(tab.getPosition());
                }

                @Override
                public void onTabUnselected(TabLayout.Tab tab) {
                    int pos = tab.getPosition();
                }

                @Override
                public void onTabReselected(TabLayout.Tab tab) {

                }
            });
        }
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(pager));
        return root;
    }
}



public class ViewPagerAdapter extends FragmentPagerAdapter  {


    ArrayList<ConnectedBluetoothDevice> devicesList;
    ArrayList<DataViewFragment> dataViewFragments;

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

    /**
     * Initializes the adaptor with the device list and the list of data fragments.
     * @param devicesList List of devices to be displayed in their own data fragment.
     */
    public void setDevicesList(ArrayList<ConnectedBluetoothDevice> devicesList) {
        this.devicesList = devicesList;
        dataViewFragments = new ArrayList<>();
        for (int i = 0; i < devicesList.size(); i++) {
            dataViewFragments.add(new DataViewFragment(devicesList.get(i)));
        }
    }

    /**
     * GetItem
     * @param position position of item in the viewPager list to be returned
     * @return fragment to view
     */
    @NonNull
    public Fragment getItem(int position) {
        if (dataViewFragments != null && position < dataViewFragments.size()) {
            return dataViewFragments.get(position);
        } else {
            return new DataViewFragment(null);
        }
    }

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

    /**
     * Updates the tabs in tabLayout while swiping pages
     * @param position of the viewPage
     * @return title of the tab
     */
    public CharSequence getPageTitle(int position) {
        super.getPageTitle(position);
        return devicesList.get(position).getName();
    }

    public void clear() {
        dataViewFragments.clear();
    }
}

Some notes:

• I’m instructed to fix this bug in ViewPager and FragmentPagerAdapter, so please don’t recommend me solutions in ViewPager2 and FragmentStatePagerAdapter 🙂
• I heard that setOffscreenPageLimit(0); isn’t the best practice so I want to avoid that situation (especially since I only need to pause the fragment but not destroy it)