Utils class for viewpager adapter with fragment content

ViewPagerFragmentAdapter

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.text.TextUtils;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * Created by CUSDungVT on 8/26/2016.
 */

public class ViewPagerFragmentAdapter extends FragmentPagerAdapter{

    private final List<Fragment> mFragments = new ArrayList<>();
    private final Map<Integer, String> mTags = new HashMap<>();
    private final List<CharSequence> mTitles = new ArrayList<>();
    private Bundle mSavedInstanceState = new Bundle();
    private final FragmentManager mFragmentManager;

    public ViewPagerFragmentAdapter(FragmentManager fm) {
        super(fm);
        mFragmentManager = fm;
    }

    @Override
    public Fragment getItem(int position) {
        String tagName = mSavedInstanceState.getString(makeTagName(position));
        if (!TextUtils.isEmpty(tagName)) {
            Fragment fragment = mFragmentManager.findFragmentByTag(tagName);
            return fragment != null ? fragment : mFragments.get(position);
        }
        return mFragments.get(position);
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        Object object = super.instantiateItem(container, position);
        mTags.put(position, ((Fragment) object).getTag());
        return object;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mTitles.get(position);
    }

    public void onRestoreInstanceState(Bundle savedInstanceState) {
        mSavedInstanceState = savedInstanceState != null ? savedInstanceState : new Bundle();
    }
    public void onSaveInstanceState(Bundle outState) {
        Iterator<Map.Entry<Integer, String>> iterator = mTags.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, String> entry = iterator.next();
            outState.putString(makeTagName(entry.getKey()), entry.getValue());
        }
    }
    public void addFragment(CharSequence title, Fragment fragment) {
        mTitles.add(title);
        mFragments.add(fragment);
    }

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

    private static String makeTagName(int position) {
        return ViewPagerFragmentAdapter.class.getName() + ":" + position;
    }
}