RecyclerView HeaderAdapter

HeaderAdapter

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public abstract class HeaderAdapter extends RecyclerView.Adapter<ViewHolder> {

    private static final String TAG = "HeaderAdapter";

    protected static final int HEADER = 0;

    private List<BaseModel> mDataset = new ArrayList<BaseModel>();
    private List<ViewHolder> mHeaders = new ArrayList<ViewHolder>();
    //map of type to position
    private Map<Integer, Integer> mHeaderTypes = new HashMap<Integer, Integer>();

    private ImageManager mImageManager;
    private LayoutInflater mInflater;
    private Context mContext;

    public HeaderAdapter(Context context, ImageManager imageManager) {
        mImageManager = imageManager;
        mInflater = LayoutInflater.from(context);
        mContext = context;
        setHasStableIds(true);
    }

    public ImageManager getImageManager() {
        return mImageManager;
    }

    public LayoutInflater getInflater() {
        return mInflater;
    }

    public Context getContext() {
        return mContext;
    }

    /**
     * Setup major data set which would be a collection items
     * */
    public void setDataset(List<BaseModel> dataset) {
        mDataset = dataset;
        notifyDataSetChanged();
    }

    public List<BaseModel> getDataset(){
        return mDataset;
    }

    public void addHeader(ViewHolder header){
        mHeaders.add(header);
        mHeaderTypes.put(getHeaderTypeForPosition(mHeaders.size() - 1), mHeaders.size() - 1);
        notifyDataSetChanged();
    }

    public void clearHeaders(){
        mHeaders.clear();
        mHeaderTypes.clear();
        notifyDataSetChanged();
    }

    @Override
    public final ViewHolder onCreateViewHolder(final ViewGroup parent, final int type) {
        if(type <= HEADER){
            final ViewHolder holder = mHeaders.get(mHeaderTypes.get(type));
            if(holder.itemView.getParent() != null){
                ((ViewGroup)holder.itemView.getParent()).removeView(holder.itemView);
            }
            return holder;
        } else {
            return onCreateHolder(parent, type);
        }
    }

    public abstract ViewHolder onCreateHolder(ViewGroup parent, int type);

    @Override
    public final void onBindViewHolder(final ViewHolder viewHolder, final int position) {
        //headers don't need to be bound they static views unrelated to dataset.
        if(!isHeader(position)){
            onBindHolder(viewHolder, (position - mHeaders.size()));
        }
    }

    public abstract void onBindHolder(ViewHolder viewHolder, int position);

    @Override
    public int getItemCount() {
        return mDataset.size() + mHeaders.size();
    }

    public int getHeaderCount(){
        return mHeaders.size();
    }

    @Override
    public final int getItemViewType(final int position) {
        if (isHeader(position)) {
            return getHeaderTypeForPosition(position);
        } else {
            return getItemType((position - mHeaders.size()));
        }
    }

    public abstract int getItemType(int position);

    @Override
    public long getItemId(int position) {
        if(isHeader(position)){
            return position; //TODO something better to return?
        } else {
            return getIdForPos(position - mHeaders.size());
        }
    }

    public abstract long getIdForPos(int position);

    /**
     * Method returns true if position of item into headers set
     * */
    private boolean isHeader(final int position) {
        return !mHeaders.isEmpty()
                && position < mHeaders.size();
    }

    private int getHeaderTypeForPosition(final int position){
        return HEADER - position;
    }

    @Override
    public void onViewDetachedFromWindow(ViewHolder holder) {
        super.onViewDetachedFromWindow(holder);
        holder.onDetachedFromWindow();
    }

    @Override
    public void onViewAttachedToWindow(ViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        holder.onAttachedToWindow();
    }

    @Override
    public void onViewRecycled(ViewHolder holder) {
        super.onViewRecycled(holder);
    }

}