StickyHeaderAdapter impl for Mike

StickyHeaderActivity.java

package com.paramsen.testground;

import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
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.ArrayList;
import java.util.List;

import butterknife.BindView;
import butterknife.ButterKnife;
import ca.barrenechea.widget.recyclerview.decoration.StickyHeaderAdapter;
import ca.barrenechea.widget.recyclerview.decoration.StickyHeaderDecoration;

public class StickyHeaderActivity extends AppCompatActivity {
    @BindView(R.id.recycler)
    RecyclerView recycler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sticky_header);
        ButterKnife.bind(this);

        TestStickyAdapter adapter = new TestStickyAdapter(this, generateItems());

        recycler.setLayoutManager(new LinearLayoutManager(this));
        recycler.addItemDecoration(new StickyHeaderDecoration(adapter));
        recycler.setAdapter(adapter);
    }

    private List<Item> generateItems() {
        List<Item> items = new ArrayList<>();

        for (int i = 1; i <= 50; i++) {
            items.add(new Item(i, i / 10 + 1));
        }

        return items;
    }

    public static class TestStickyAdapter extends RecyclerView.Adapter<ViewHolder> implements StickyHeaderAdapter<HeaderHolder> {
        private LayoutInflater mInflater;
        private List<Item> items;

        public TestStickyAdapter(Context context, List<Item> items) {
            mInflater = LayoutInflater.from(context);
            this.items = items;
        }

        @Override
        public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
            final View view = mInflater.inflate(R.layout.item_test, viewGroup, false);

            return new ViewHolder(view);
        }

        @Override
        public void onBindViewHolder(ViewHolder viewHolder, int position) {
            viewHolder.item.setText("Item " + items.get(position).position);
        }

        @Override
        public int getItemCount() {
            return items.size();
        }

        @Override
        public long getHeaderId(int position) {
            return (long) items.get(position).header;
        }

        @Override
        public HeaderHolder onCreateHeaderViewHolder(ViewGroup parent) {
            final View view = mInflater.inflate(R.layout.header_test, parent, false);
            return new HeaderHolder(view);
        }

        @Override
        public void onBindHeaderViewHolder(HeaderHolder viewholder, int position) {
            viewholder.header.setText("Header " + items.get(position).header);
        }
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView item;

        public ViewHolder(View itemView) {
            super(itemView);

            item = (TextView) itemView;
        }
    }

    public static class HeaderHolder extends RecyclerView.ViewHolder {
        public TextView header;

        public HeaderHolder(View itemView) {
            super(itemView);

            header = (TextView) itemView;
        }
    }

    private class Item {
        public final int position;
        public final int header;

        private Item(int position, int header) {
            this.position = position;
            this.header = header;
        }
    }
}