How do you add a header and footer to a RecyclerView without getting a NullPointerException?

Implementing Headers and Footers in RecyclerView

Problem:

Adding a header or footer to a RecyclerView can be a challenge. The code provided suggests adding a view to the LinearLayoutManager using addView(View view, int position), but this approach was not successful and resulted in a NullPointerException.

Solution:

Adding a Footer

To add a footer to a RecyclerView, follow these steps:

• Create a ViewHolder for the footer view.
• Override onCreateViewHolder to inflate the footer view when necessary.
• Override onBindViewHolder to bind data to the footer view.
• Override getItemCount to include the footer in the count.
• Override getItemViewType to distinguish the footer from the normal list items.

Example Footer Adapter:

public class FooterViewHolder extends RecyclerView.ViewHolder {
    public FooterViewHolder(View itemView) {
        super(itemView);
    }
}

public class RecyclerViewWithFooterAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private static final int FOOTER_VIEW = 1;
    private List<String> data;

    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size() + 1;
    }

    @Override
    public int getItemViewType(int position) {
        return position == data.size() ? FOOTER_VIEW : super.getItemViewType(position);
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v;
        if (viewType == FOOTER_VIEW) {
            v = LayoutInflater.from(context).inflate(R.layout.list_item_footer, parent, false);
            return new FooterViewHolder(v);
        }
        v = LayoutInflater.from(context).inflate(R.layout.list_item_normal, parent, false);
        return new NormalViewHolder(v);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof FooterViewHolder) {
            FooterViewHolder vh = (FooterViewHolder) holder;
        } else {
            NormalViewHolder vh = (NormalViewHolder) holder;
            vh.bindView(position);
        }
    }
}

Adding a Header

Adding a header to a RecyclerView follows a similar process:

• Create a ViewHolder for the header view.
• Override onCreateViewHolder to inflate the header view when necessary.
• Add the header view to the RecyclerView using RecyclerView.addHeaderView(View view).
• Override getItemCount to include the header in the count.

Additional Notes:

• If you need multiple headers and footers, handle them similarly by adjusting the getItemViewType and getItemCount methods.
• The provided GitHub repository offers a complete implementation of adding both headers and footers.

The above is the detailed content of How do you add a header and footer to a RecyclerView without getting a NullPointerException?. For more information, please follow other related articles on the PHP Chinese website!