Parent Fragment

package me.kaidul.uhunt;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

import me.kaidul.uhunt.ChaptersListFragment.OnChapterSelectListener;
import me.kaidul.uhunt.SubChaptersListFragment.OnSubChapterSelectListener;
import me.kaidul.uhunt.SubSubChaptersListFragment.OnSubSubChapterSelectListener;

import com.devspark.progressfragment.SherlockProgressFragment;
import com.google.gson.stream.JsonReader;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class CompetitiveProgramming extends SherlockProgressFragment implements
        OnChapterSelectListener, OnSubChapterSelectListener, OnSubSubChapterSelectListener {

    View mContentView;
    static public List<Chapter> chapterList = new ArrayList<Chapter>();

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

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setContentView(mContentView);
        setContentShown(false);
        new ProcessTask().execute();
    }

    @Override
    public void onDetach() {
        super.onDetach();

        try {
            Field childFragmentManager = Fragment.class
                    .getDeclaredField("mChildFragmentManager");
            childFragmentManager.setAccessible(true);
            childFragmentManager.set(this, null);

        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }

    protected class ProcessTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... params) {
            // other stuffs
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            Fragment chapterFragment = new ChaptersListFragment();
            Fragment subChapterFragment = new SubChaptersListFragment();
            Fragment subSubChapterFragment = new SubSubChaptersListFragment();
            FragmentTransaction transaction = getChildFragmentManager()
                    .beginTransaction();
            transaction.add(R.id.category_fragment, chapterFragment);
            transaction.add(R.id.sub_category_fragment, subChapterFragment);
            transaction.add(R.id.sub_sub_category_fragment,
                    subSubChapterFragment);
            transaction.commit();
            setContentShown(true);
        }

    }

    @Override
    public void onChapterSelected(int position) {
        SubChaptersListFragment subChapterFrag = new SubChaptersListFragment();
        if ( subChapterFrag != null) {
            subChapterFrag.updateList(position);
        } else {

        }

    }

    @Override
    public void onSubChapterSelected(int prev, int position) {
        SubSubChaptersListFragment subSubChapterFrag = new SubSubChaptersListFragment();
        if (subSubChapterFrag != null) {
            subSubChapterFrag.updateList(prev, position);
        } else {
            // nothing now
        }
    }

    @Override
    public void onSubSubChapterSelected(int prev, int nextPrev, int position) {
    }

}