How to implement RecyclerView with section header depending on category?

Question

I want to implement sections in my list. I have a list of tasks. List has a custom adapter which extends recyclerview swipe adapter as I have implemented swipe gesture to th

Answer 1

The most simple way to split your recycler view into sections is by using a layout with the header and the item already in place and then changing the visibility if the header is the same.

Layout:

Adapter (2018 Kotlin Edition):

class ContactAdapter @Inject constructor() : RecyclerView.Adapter() {

    var onItemClick: ((Contact) -> Unit)? = null
    var contacts = emptyList()

    override fun getItemCount(): Int {
        return contacts.size
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.item_contact, parent, false))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val name = contacts[position].name
        holder.header.text = name.substring(0, 1)
        holder.name.text = name

        // if not first item, check if item above has the same header
        if (position > 0 && contacts[position - 1].name.substring(0, 1) == name.substring(0, 1)) {
            holder.headerTextView.visibility = View.GONE
        } else {
            holder.headerTextView.visibility = View.VISIBLE
        }
    }

    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val headerTextView: TextView = itemView.tvHeader
        val nameTextView: TextView = itemView.tvName

        init {
            itemView.setOnClickListener {
                onItemClick?.invoke(contacts[adapterPosition])
            }
        }
    }
}

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Might be helpful as well: RecyclerView itemClickListener in Kotlin

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Old Java Adapter Version:

public class RecyclerAdapter extends RecyclerView.Adapter {

    private List mData;

    @Inject
    public RecyclerAdapter() {
        mData = new ArrayList<>();
    }

    public void setData(List data) {
        mData = data;
    }

    public Contact getItem(int position){
        return mData.get(position);
    }

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

    @Override
    public void onBindViewHolder(final DataViewHolder holder, int position) {
        Contact contact = mData.get(position);
        holder.headerTextView.setText(contact.getName().substring(0, 1));
        holder.nameTextView.setText(contact.getName());

        // if not first item check if item above has the same header
        if (position > 0 && mData.get(position - 1).getName().substring(0, 1).equals(contact.getName().substring(0, 1))) {
            holder.headerTextView.setVisibility(View.GONE);
        } else {
            holder.headerTextView.setVisibility(View.VISIBLE);
        }
    }

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

    public class DataViewHolder extends RecyclerView.ViewHolder {

        @BindView(R.id.text_header)
        TextView headerTextView;
        @BindView(R.id.text_name)
        TextView nameTextView;

        public DataViewHolder(View itemView) {
            super(itemView);
            ButterKnife.bind(this, itemView);
        }
    }
}