Tiny app to demonstrate nested RecyclerViews

activity_main.xml

<android.support.v7.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/list"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

category.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

item.xml

<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="4dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="4dp"
            tools:text="title"/>

        <ImageView
            android:id="@+id/image"
            android:layout_width="120dp"
            android:layout_height="80dp"/>

    </LinearLayout>

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

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView recycler = findViewById(R.id.list);
        recycler.setLayoutManager(new LinearLayoutManager(this));
        recycler.setAdapter(new CategoriesAdapter());
    }

    private static class CategoriesAdapter extends RecyclerView.Adapter<CategoryViewHolder> {

        @Override
        public CategoryViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater inflater = LayoutInflater.from(parent.getContext());
            View itemView = inflater.inflate(R.layout.category, parent, false);
            return new CategoryViewHolder(itemView);
        }

        @Override
        public void onBindViewHolder(CategoryViewHolder holder, int position) {
            holder.title.setText("category: " + position);
            holder.recycler.setAdapter(new ItemsAdapter());
        }

        @Override
        public int getItemCount() {
            return 100;
        }
    }

    private static class CategoryViewHolder extends RecyclerView.ViewHolder {

        private final TextView title;
        private final RecyclerView recycler;

        private CategoryViewHolder(View itemView) {
            super(itemView);

            this.title = itemView.findViewById(R.id.title);
            this.recycler = itemView.findViewById(R.id.list);

            recycler.setLayoutManager(new LinearLayoutManager(itemView.getContext(), LinearLayoutManager.HORIZONTAL, false));
        }
    }

    private static class ItemsAdapter extends RecyclerView.Adapter<ItemViewHolder> {

        @Override
        public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater inflater = LayoutInflater.from(parent.getContext());
            View itemView = inflater.inflate(R.layout.item, parent, false);
            return new ItemViewHolder(itemView);
        }

        @Override
        public void onBindViewHolder(ItemViewHolder holder, int position) {
            holder.title.setText("item: " + position);

            int number = (position % 10) + 1;
            String url = "http://lorempixel.com/400/200/cats/" + number + "/";

            Picasso.with(holder.itemView.getContext())
                   .load(url)
                   .into(holder.image);
        }

        @Override
        public int getItemCount() {
            return 50;
        }
    }

    private static class ItemViewHolder extends RecyclerView.ViewHolder {

        private final TextView title;
        private final ImageView image;

        private ItemViewHolder(View itemView) {
            super(itemView);

            this.title = itemView.findViewById(R.id.title);
            this.image = itemView.findViewById(R.id.image);
        }
    }
}

Thanks It is very Helpful