How to save current state of the Activity and a Fragment

Question

I am new in Android development, I am building an onboarding screen and I created MainActivity Which creates ViewPager2 and sets an adapter FragmentStateAdapter my ISSUE is when I change the theme to dark the app crashes the error is

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.zamw.onboarding/com.zamw.onboarding.MainActivity}: androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.zamw.onboarding.OnboardingFragment: could not find Fragment constructor

Below is My MainActivity and Fragment files

package com.zamw.onboarding;

import androidx.appcompat.app.AppCompatActivity;
import androidx.cardview.widget.CardView;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;
import android.util.DisplayMetrics;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private static final int NUM_PAGES = 4;
    private ViewPager2 viewPager;
    private FragmentStateAdapter pagerAdapter;
    private CardView[] dots;
    private TextView textView;
    private LinearLayout.LayoutParams layoutParams;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = findViewById(R.id.pager);
        textView = findViewById(R.id.skip);
        dots = new CardView[]{findViewById(R.id.dot1),
                findViewById(R.id.dot2),
                findViewById(R.id.dot3),
                findViewById(R.id.dot4)};

        viewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);
                for (int i=0; i<4; i++)
                {
                    layoutParams = (LinearLayout.LayoutParams) dots[i].getLayoutParams();
                    if (i==position) {
                           dots[i].setCardBackgroundColor(getResources().getColor(R.color.colorPrimaryDark));
                           layoutParams.height=dpToPx(8);
                           layoutParams.width=dpToPx(20);
                           dots[i].setLayoutParams(layoutParams);
                           if (position==3){textView.setText("GET STARTED");}
                    }
                    else  {
                        dots[i].setCardBackgroundColor(getResources().getColor(R.color.red));
                        layoutParams.height=dpToPx(8);
                        layoutParams.width=dpToPx(8);
                        dots[i].setLayoutParams(layoutParams);
                        textView.setText("SKIP");
                    }
                }
            }
        });

        pagerAdapter = new ScreenSlidePagerAdapter(this);

        viewPager.setAdapter(pagerAdapter);

    }

    public int dpToPx(int dp) {
        DisplayMetrics displayMetrics = this.getResources().getDisplayMetrics();
        return Math.round(dp * (displayMetrics.xdpi / DisplayMetrics.DENSITY_DEFAULT));
    }

    private class ScreenSlidePagerAdapter extends FragmentStateAdapter {
        public ScreenSlidePagerAdapter(FragmentActivity fa) {
            super(fa);
        }

        @Override
        public Fragment createFragment(int position) {
            OnboardingFragment fragment = new OnboardingFragment(position);
            return fragment;
        }

        @Override
        public int getItemCount() {
            return NUM_PAGES;
        }
    }
}
     

Fragment

package com.zamw.onboarding;

import android.os.Bundle;

import androidx.cardview.widget.CardView;
import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class OnboardingFragment extends Fragment {

    private int infoId;

    public OnboardingFragment(int infoId){
        this.infoId=infoId;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_onboarding, container, false);
    }

    @Override
    public void onStart() {
        super.onStart();
        View view = getView();
        if (view!=null){
            Informations informations = Informations.informations[infoId];

            ImageView imageView = view.findViewById(R.id.imageView);
            imageView.setImageResource(informations.getImageID());

            TextView title = view.findViewById(R.id.textTitle);
            title.setText(informations.getName());

            TextView description = view.findViewById(R.id.textDescription);
            description.setText(informations.getDescription());
        }
    }
}

I want to know how to handle this kind of problems, how to save current state of the screen?