MyPagerAdapter

package yuvallevy.testrecyclerview;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;

import java.util.ArrayList;
import java.util.List;

import yuvallevy.testrecyclerview.Interfaces.Tab1MainFragmentListner;

public class MyPagerAdapter extends FragmentStatePagerAdapter {

    private List<Fragment> fragmentList = new ArrayList<>();
    private List<String> fragmentTitleList = new ArrayList<>();
    private Fragment mFragmentAtPos0;
    private FragmentManager mFragmentManger;

    static final int NUM_ITEMS = 3;

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

    @Override
    public Fragment getItem(int pos) {

        if(pos == 0){
            if(mFragmentAtPos0 == null){
               return mFragmentAtPos0 = Tab1MainView.newInstance();
            }else{
                return mFragmentAtPos0;
            }
        }else {
            return fragmentList.get(pos);
        }

    }

    @Override
    public int getItemPosition(Object object) {
        if(object instanceof CategorySelected){
            return POSITION_NONE;
        }else if(object instanceof Tab1Fragment){
            return POSITION_NONE;
        }else {
            return POSITION_UNCHANGED;
        }

    }

    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

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

    public void addFragment(Fragment fragment, String title){
        fragmentList.add(fragment);
        fragmentTitleList.add(title);
    }

    public final class Tab1Fragment implements Tab1MainFragmentListner{

        @Override
        public void onSwitchToNextFragment(int pos) {
            mFragmentManger.beginTransaction().remove(mFragmentAtPos0).commit();
            mFragmentAtPos0 =  CategorySelected.newInstance(pos);
            notifyDataSetChanged();
        }
    }


}