HeaderFooterRecyclerViewWrapperAdapter.java

import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.ViewGroup;

public abstract class HeaderFooterRecyclerViewWrapperAdapter<HeaderViewHolder extends RecyclerView.ViewHolder,
        FooterViewHolder extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private static final int VIEW_TYPE_MASK = 0xfffffff;
    private static final int VIEW_TYPE_HEADER = 0x10000000;
    private static final int VIEW_TYPE_FOOTER = 0x20000000;

    private final RecyclerView.Adapter wrappedAdapter;
    private int headerItemCount;
    private int footerItemCount;
    private int contentItemCount;

    public HeaderFooterRecyclerViewWrapperAdapter(@NonNull RecyclerView.Adapter wrappedAdapter) {
        this.wrappedAdapter = wrappedAdapter;
        wrappedAdapter.registerAdapterDataObserver(dataObserver);

        setHasStableIds(wrappedAdapter.hasStableIds());
    }

    @Override
    public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if ((viewType & VIEW_TYPE_HEADER) != 0) {
            return onCreateHeaderItemViewHolder(parent, viewType & VIEW_TYPE_MASK);
        } else if ((viewType & VIEW_TYPE_FOOTER) != 0) {
            return onCreateFooterItemViewHolder(parent, viewType & VIEW_TYPE_MASK);
        } else {
            return wrappedAdapter.onCreateViewHolder(parent, viewType & VIEW_TYPE_MASK);
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    public final void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (position < headerItemCount) {
            onBindHeaderItemViewHolder((HeaderViewHolder)holder, position);
        } else if (position < headerItemCount + contentItemCount) {
            wrappedAdapter.onBindViewHolder(holder, position);
        } else if (position < headerItemCount + contentItemCount + footerItemCount) {
            onBindFooterItemViewHolder((FooterViewHolder)holder, position);
        } else {
            throw new IllegalStateException("Item position is invalid");
        }
    }

    @Override
    public final int getItemCount() {
        headerItemCount = getHeaderItemCount();
        footerItemCount = getFooterItemCount();
        contentItemCount = wrappedAdapter.getItemCount();
        return headerItemCount + contentItemCount + footerItemCount;
    }

    @Override
    public final int getItemViewType(int position) {
        if (position < headerItemCount) {
            return (getHeaderItemViewType() & VIEW_TYPE_MASK) | VIEW_TYPE_HEADER;
        } else if (position < headerItemCount + contentItemCount) {
            return wrappedAdapter.getItemViewType(position) & VIEW_TYPE_MASK;
        } else if (position < headerItemCount + contentItemCount + footerItemCount) {
            return (getFooterItemViewType() & VIEW_TYPE_MASK) | VIEW_TYPE_FOOTER;
        } else {
            throw new IllegalStateException("Item position is invalid");
        }
    }

    @Override
    public final long getItemId(int position) {
        if (!hasStableIds()) {
            return RecyclerView.NO_ID;
        }
        if (position < headerItemCount) {
            return RecyclerView.NO_ID; // TODO:
        } else if (position < headerItemCount + contentItemCount) {
            return wrappedAdapter.getItemId(position);
        } else if (position < headerItemCount + contentItemCount + footerItemCount) {
            return RecyclerView.NO_ID; // TODO:
        } else {
            throw new IllegalStateException("Item position is invalid");
        }
    }

    public final void notifyHeaderItemChanged(int position) {
        if (position < 0 || position >= headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item position " + position + " is invalid");
        }
        notifyItemChanged(position);
    }

    public final void notifyHeaderItemRangeChanged(int positionStart, int itemCount) {
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeChanged(positionStart, itemCount);
    }

    public final void notifyHeaderItemInserted(int position) {
        final int headerItemCount = getHeaderItemCount();
        if (position < 0 || position >= headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item position " + position + " is invalid");
        }
        notifyItemInserted(position);
    }

    public final void notifyHeaderItemRangeInserted(int positionStart, int itemCount) {
        final int headerItemCount = getHeaderItemCount();
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeInserted(positionStart, itemCount);
    }

    public final void notifyHeaderItemMoved(int fromPosition, int toPosition) {
        if (fromPosition < 0 || toPosition < 0 || fromPosition >= headerItemCount || toPosition >= headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item fromPosition " + fromPosition + " or toPosition " + toPosition + " is invalid");
        }
        notifyItemMoved(fromPosition, toPosition);
    }

    public final void notifyHeaderItemRemoved(int position) {
        if (position < 0 || position >= headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item position " + position + " is invalid");
        }
        notifyItemRemoved(position);
    }

    public final void notifyHeaderItemRangeRemoved(int positionStart, int itemCount) {
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > headerItemCount) {
            throw new IndexOutOfBoundsException("The specified header item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeRemoved(positionStart, itemCount);
    }

    public final void notifyFooterItemChanged(int position) {
        if (position < 0 || position >= footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item position " + position + " is invalid");
        }
        notifyItemChanged(position + headerItemCount + contentItemCount);
    }

    public final void notifyFooterItemRangeChanged(int positionStart, int itemCount) {
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeChanged(positionStart + headerItemCount + contentItemCount, itemCount);
    }

    public final void notifyFooterItemInserted(int position) {
        final int headerItemCount = getHeaderItemCount();
        final int footerItemCount = getFooterItemCount();
        final int contentItemCount = wrappedAdapter.getItemCount();
        if (position < 0 || position >= footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item position " + position + " is invalid");
        }
        notifyItemInserted(position + headerItemCount + contentItemCount);
    }

    public final void notifyFooterItemRangeInserted(int positionStart, int itemCount) {
        final int headerItemCount = getHeaderItemCount();
        final int footerItemCount = getFooterItemCount();
        final int contentItemCount = wrappedAdapter.getItemCount();
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeInserted(positionStart + headerItemCount + contentItemCount, itemCount);
    }

    public final void notifyFooterItemMoved(int fromPosition, int toPosition) {
        if (fromPosition < 0 || toPosition < 0 || fromPosition >= footerItemCount || toPosition >= footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item fromPosition " + fromPosition + " or toPosition " + toPosition + " is invalid");
        }
        notifyItemMoved(fromPosition + headerItemCount + contentItemCount, toPosition + headerItemCount + contentItemCount);
    }

    public final void notifyFooterItemRemoved(int position) {
        if (position < 0 || position >= footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item position " + position + " is invalid");
        }
        notifyItemRemoved(position + headerItemCount + contentItemCount);
    }

    public final void notifyFooterItemRangeRemoved(int positionStart, int itemCount) {
        if (positionStart < 0 || itemCount < 0 || positionStart + itemCount > footerItemCount) {
            throw new IndexOutOfBoundsException("The specified footer item range " + positionStart + ".." + (positionStart + itemCount - 1) + " is invalid");
        }
        notifyItemRangeRemoved(positionStart + headerItemCount + contentItemCount, itemCount);
    }

    private final RecyclerView.AdapterDataObserver dataObserver = new RecyclerView.AdapterDataObserver() {
        @Override
        public void onChanged() {
            notifyDataSetChanged();
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount) {
            notifyItemRangeChanged(headerItemCount + positionStart, itemCount);
        }

        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            notifyItemRangeInserted(headerItemCount + positionStart, itemCount);
        }

        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            notifyItemRangeRemoved(headerItemCount + positionStart, itemCount);
        }

        @Override
        public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
            for (int i = 0; i < itemCount; i++) {
                notifyItemMoved(headerItemCount + fromPosition, headerItemCount + toPosition);
            }
        }
    };

    public int getHeaderItemCount() {
        return 0;
    }

    public int getFooterItemCount() {
        return 0;
    }

    public int getHeaderItemViewType() {
        return 0;
    }

    public int getFooterItemViewType() {
        return 0;
    }

    public HeaderViewHolder onCreateHeaderItemViewHolder(ViewGroup parent, int viewType) {
        throw new RuntimeException("This method should be overridden in derived class");
    }

    public FooterViewHolder onCreateFooterItemViewHolder(ViewGroup parent, int viewType) {
        throw new RuntimeException("This method should be overridden in derived class");
    }

    public void onBindHeaderItemViewHolder(HeaderViewHolder holder, int position) {
    }

    public void onBindFooterItemViewHolder(FooterViewHolder holder, int position) {
    }
}