BaseRecyclerViewAdapter.java

package com.yourpackage.android;

import android.content.Context;
import android.support.annotation.CallSuper;
import android.support.annotation.IdRes;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import com.yourpackage.android.R;

import java.util.ArrayList;

/**
 * Handles putting headers and footers on a recyclerview
 */
public abstract class BaseRecyclerViewAdapter<T extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    LayoutInflater inflater;

    private final ArrayList<View> headerViews;
    private final ArrayList<View> footerViews;

    private boolean headerShouldSpanView = true;
    private boolean footerShouldSpanView = true;
    private final int headerViewType;
    private final int footerViewType;

    @CallSuper
    public void addHeaderView(View headerView) {
        this.headerViews.add(headerView);
    }

    @CallSuper
    void removeHeaderView(View headerView) {
        this.headerViews.remove(headerView);
    }

    @CallSuper
    public void addFooterView(View footerView) {
        this.footerViews.add(footerView);
    }

    @CallSuper
    void removeFooterView(View footerView) {
        this.footerViews.remove(footerView);
    }

    private boolean isListHeaderPosition(int position) {
        return position < headerViews.size();
    }

    private boolean isListFooterPosition(int position) {
        return position >= getListItemCount() + headerViews.size();
    }

    /**
     * @param context - activity context
     * @param headerViewType -- must be UNIQUE; used to identify a header view
     * @param footerViewType -- must be UNIQUE; used to identify a footer view
     */
    protected BaseRecyclerViewAdapter(Context context, @IdRes int headerViewType, @IdRes int footerViewType) {
        super();
        inflater = LayoutInflater.from(context);
        this.headerViewType = headerViewType;
        this.footerViewType = footerViewType;
        headerViews = new ArrayList<>();
        footerViews = new ArrayList<>();
    }

    public static class FixedViewHolder extends RecyclerView.ViewHolder {
        public final FrameLayout frameLayout;

        public FixedViewHolder(FrameLayout view) {
            super(view);
            frameLayout = view;
        }
    }

    @Override
    public final int getItemViewType(int position) {
        if (isListHeaderPosition(position)) {
            return headerViewType;
        }

        if (isListFooterPosition(position)) {
            return footerViewType;
        }

        return getListItemViewType(convertAdapterPositionToUnderlyingListDataPosition(position));
    }

    @Override
    public final int getItemCount() {
        return headerViews.size() + footerViews.size() + getListItemCount();
    }

    @Override
    public final RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int typeView) {
        if (typeView == headerViewType || typeView == footerViewType) {
            final FrameLayout headerContainer = (FrameLayout) inflater.inflate(R.layout.empty_container, parent, false);
            return new FixedViewHolder(headerContainer);
        }

        return onCreateListItemViewHolder(parent, typeView);
    }

    public int convertAdapterPositionToUnderlyingListDataPosition(int position) {
        return position - headerViews.size();
    }

    int convertUnderlyingListDataPositionToAdapterPosition(int position) {
        return position + headerViews.size();
    }

    @Override
    public final void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        if (viewHolder instanceof FixedViewHolder) {
            if (isListHeaderPosition(position)) {
                bindNonItemView((FixedViewHolder) viewHolder, headerViews.get(position), headerShouldSpanView);
                return;
            }

            if (isListFooterPosition(position)) {
                bindNonItemView((FixedViewHolder) viewHolder, footerViews.get(getFooterIndex(position)), footerShouldSpanView);
                return;
            }

            return;
        }

        //noinspection unchecked
        onBindListItemViewHolder((T) viewHolder, convertAdapterPositionToUnderlyingListDataPosition(position));
    }

    private void bindNonItemView(FixedViewHolder viewHolder, View view, boolean shouldSpanView) {
        if (viewHolder.itemView.getLayoutParams() instanceof StaggeredGridLayoutManager.LayoutParams && shouldSpanView) {
            StaggeredGridLayoutManager.LayoutParams layoutParams = (StaggeredGridLayoutManager.LayoutParams) viewHolder.itemView.getLayoutParams();
            layoutParams.setFullSpan(true);
        }

        if (viewHolder.frameLayout.getChildCount() > 0) {
            viewHolder.frameLayout.removeAllViews();
        }

        ViewGroup parent = (ViewGroup) view.getParent();

        if (parent != null) {
            parent.removeView(view);
        }

        viewHolder.frameLayout.addView(view);

        if (viewHolder.frameLayout.getLayoutParams() instanceof StaggeredGridLayoutManager.LayoutParams && shouldSpanView) {
            StaggeredGridLayoutManager.LayoutParams layoutParams = (StaggeredGridLayoutManager.LayoutParams) viewHolder.frameLayout.getLayoutParams();
            layoutParams.setFullSpan(true);
            viewHolder.frameLayout.setLayoutParams(layoutParams);
        }
    }

    private int getFooterIndex(int position) {
        return position - getListItemCount() - headerViews.size();
    }

    @Override
    public final long getItemId(int position) {
        if (isListHeaderPosition(position) || isListFooterPosition(position)) {
            return -1;
        }

        return getListItemId(convertAdapterPositionToUnderlyingListDataPosition(position));
    }

    protected abstract RecyclerView.ViewHolder onCreateListItemViewHolder(ViewGroup parent, int typeView);

    protected abstract void onBindListItemViewHolder(T viewHolder, int position);

    protected abstract int getListItemCount();

    @IdRes
    protected abstract int getListItemViewType(int position);

    protected abstract long getListItemId(int position);

    public int getHeaderCount() {
        return headerViews != null ? headerViews.size() : 0;
    }

    public int getFooterCount() {
        return footerViews != null ? footerViews.size() : 0;
    }

    public void setHeaderShouldSpanView(boolean headerShouldSpanView) {
        this.headerShouldSpanView = headerShouldSpanView;

        if (headerViews.size() > 0) {
            notifyItemRangeChanged(0, headerViews.size() - 1);
        }
    }

    public void setFooterShouldSpanView(boolean footerShouldSpanView) {
        this.footerShouldSpanView = footerShouldSpanView;

        if (footerViews.size() > 0) {
            notifyItemRangeChanged(getItemCount() - footerViews.size() - 1, getItemCount() - 1);
        }
    }
}