How to save state in fragment

Question

I have 4 button to replace fragment in activity [fragment A , fragment B , fragment C , fragment D] and then I replace fragment A to activity and I change value in fragment A after that I replace fragment B to fragment A and replace fragment C to fragment B . But I want to replace fragment A to fragment C . How to save state in fragment A.

Code when I commit fragment

  private void beginFragmentTransaction(BaseFragment fragment) {
    String tag = fragment.getClass().getName();
    currentFragmentTag = tag;

    boolean fragmentPopped = getChildFragmentManager().popBackStackImmediate(tag, 0);

    if (!fragmentPopped) {
        getChildFragmentManager().beginTransaction()
                .replace(R.id.container, fragment, tag)
                .addToBackStack(tag)
                .commit();
    }

}

Diagram to replace

fragment A -------> fragment B

fragment B -------> fragment C

fragment C -------> fragment A

PS. I don't want to use back button to back to fragment A , I want to replace fragment A and restore data in the first commit.

Answer 1

Instead of restoring the state during onCreate() you may choose to implement onRestoreInstanceState(), which the system calls after the onStart() method. The system calls onRestoreInstanceState() only if there is a saved state to restore, so you do not need to check whether the Bundle is null.

FYI : this is a sample code. Just for your reference.

public class MainFragment extends Fragment {
private String title;
private double rating;
private int year;

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

savedInstanceState.putString(TITLE, "Gladiator");
savedInstanceState.putDouble(RATING, 8.5);
savedInstanceState.putInt(YEAR, 2000);
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);

title = savedInstanceState.getString(TITLE);
rating = savedInstanceState.getDouble(RATING);
year = savedInstanceState.getInt(YEAR);
}
}

FYI : This really a good thread check this also Once for all, how to correctly save instance state of Fragments in back stack?

Answer 2

If you want to save the state of previous tabs and don't want to refresh/recreate view use this code and change the value according to the tabs limit

ViewPager mViewPager = (ViewPager)findViewById(R.id.pager);
mViewPager.setOffscreenPageLimit(2);