RecyclerView with Headers (LinearLayout)

item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="5dp"
    android:layout_marginRight="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="@dimen/activity_horizontal_margin">

        <TextView
            android:id="@+id/text_view_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="18sp"
            android:textStyle="bold"
            tools:text="Jalebi - A Desi Word Game" />

        <TextView
            android:id="@+id/text_view_sub_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            tools:text="1M Downloads" />

    </LinearLayout>
</android.support.v7.widget.CardView>

item_header.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="@dimen/activity_horizontal_margin">

    <TextView
        android:id="@+id/text_view_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textStyle="bold"
        tools:text="Games" />

    <TextView
        android:id="@+id/text_view_sub_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        tools:text="Recommended for you" />

</LinearLayout>

sampledata.json

[
  {
    "title": "New + Updated Games",
    "desc": "Selected games of the week",
    "apps": [
      {
        "title": "Real Cricket",
        "rating": "4.1"
      },
      {
        "title": "Tower Crush",
        "rating": "4.3"
      },
      {
        "title": "Pool ZingPlay",
        "rating": "4.7"
      }
    ]
  },
  {
    "title": "Casual Games",
    "desc": "Recommended for you",
    "apps": [
      {
        "title": "Gardens  Capes",
        "rating": "4.4"
      },
      {
        "title": "Pen Fight",
        "rating": "3.9"
      }
    ]
  },
  {
    "title": "You Might Like...",
    "desc": "Based on your recent installs",
    "apps": [
      {
        "title": "FIE Sword",
        "rating": "4.6"
      },
      {
        "title": "Mad Bullets",
        "rating": "4.3"
      },
      {
        "title": "50 50",
        "rating": "4.1"
      },
      {
        "title": "Sine Line",
        "rating": "4.7"
      },
      {
        "title": "Sine Line",
        "rating": "4.7"
      }
    ]
  }
]

Section.java

public class Section {

    public String title;
    public String desc;
    public List<App> apps;

    public class App {
        public String title;
        public String rating;
    }
}

SectionedRecyclerAdapter.java

package com.prasanna.recyclerview.samples;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.LinkedList;
import java.util.List;

/**
 * Created by prasanna on 23/10/16.
 */

public class SectionedRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private List<Section> mSections;

    private List<Position> mActualPositions;
    private OnChildItemClickListener mOnChildItemClickListener;
    private OnHeaderClickListener mOnHeaderClickListener;

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType) {
            case R.layout.item_header:
                return new HeaderViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.item_header, parent, false));
            case R.layout.item:
                return new ItemViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.item, parent, false));
            default:
                return null;
        }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        Position pos = mActualPositions.get(position);
        if (pos.child == -1) {
            HeaderViewHolder headerView = (HeaderViewHolder) holder;
            headerView.textViewTitle.setText(mSections.get(pos.header).title);
            headerView.textViewSubTitle.setText(mSections.get(pos.header).desc);
        } else {
            ItemViewHolder itemView = (ItemViewHolder) holder;
            itemView.textViewTitle.setText(mSections.get(pos.header).apps.get(pos.child).title);
            itemView.textViewRating.setText(mSections.get(pos.header).apps.get(pos.child).rating);
        }
    }

    @Override
    public int getItemViewType(int position) {
        return isHeader(position) ? R.layout.item_header : R.layout.item;
    }

    @Override
    public int getItemCount() {
        if (mSections == null) return 0;

        int count = 0;
        count = mSections.size();
        for (Section section : mSections) {
            count = count + section.apps.size();
        }
        return count;
    }

    public void setData(List<Section> sections) {
        mSections = sections;
        int headers = sections.size();

        mActualPositions = new LinkedList<>();

        for (int i = 0; i < headers; i++) {
            int size = mSections.get(i).apps.size();

            for (int j = -1; j < size; j++) {
                mActualPositions.add(new Position(i, j));
            }
        }

        notifyDataSetChanged();
    }

    private boolean isHeader(int pos) {
        return mActualPositions.get(pos).child == -1;
    }

    public void setOnChildItemClickListener(OnChildItemClickListener listener) {
        mOnChildItemClickListener = listener;

    }

    public void setOnHeaderClickListener(OnHeaderClickListener listener) {
        mOnHeaderClickListener = listener;
    }

    private class Position {
        int header;
        int child;

        Position(int header, int child) {
            this.header = header;
            this.child = child;
        }
    }

    private class ItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        final TextView textViewTitle;
        final TextView textViewRating;

        ItemViewHolder(View itemView) {
            super(itemView);

            textViewTitle = (TextView) itemView.findViewById(R.id.text_view_title);
            textViewRating = (TextView) itemView.findViewById(R.id.text_view_sub_title);

            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            if (mOnChildItemClickListener == null) return;

            Position position = mActualPositions.get(getAdapterPosition());
            mOnChildItemClickListener.onChildItemClicked(position.header, position.child);
        }
    }

    private class HeaderViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        final TextView textViewTitle;
        final TextView textViewSubTitle;

        HeaderViewHolder(View itemView) {
            super(itemView);

            textViewTitle = (TextView) itemView.findViewById(R.id.text_view_title);
            textViewSubTitle = (TextView) itemView.findViewById(R.id.text_view_sub_title);

            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            if (mOnHeaderClickListener == null) return;

            Position position = mActualPositions.get(getAdapterPosition());
            mOnHeaderClickListener.onHeaderClicked(position.header);
        }
    }

    public interface OnChildItemClickListener {
        void onChildItemClicked(int header, int child);
    }

    public interface OnHeaderClickListener {
        void onHeaderClicked(int header);
    }
}