How do I implement Fragment data in Android ViewPager?

If you want to save the state value when the fragment is terminated, inherit the FragmentStatePagerAdapter and create an adapter. You can then override the fragment's onSaveInstanceState. The onSaveInstanceState function can store data in the Bundle that is called before the fragment is terminated and passed to the parameter, and eject the data stored in the Bundle in the onCreate/onCreateView when the fragment is generated again.

Fragment (Pseudo-code)

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    if (savedInstanceState != null && savedInstanceState.get("data") != null) {
       // Use previously stored data
       ...

    }
    return view;
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    // Save Data
    outState.putInt("data", "XXX");
}

In addition, if you have a fixed number of pages in ViewPager and want to keep the fragments in memory when swiping, use the setOffscreenPageLimit(intlimit) function in ViewPager. This is the easiest way to maintain the state of the fragment.