RetrieveHeaderView.java

package com.zulip.android.viewholders.stickyheaders;

import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.RecyclerView;
import android.view.ViewGroup;

import com.zulip.android.ZulipApp;

public class RetrieveHeaderView {

    public static int DEFAULT_VIEW_TYPE = -1;

    private final RecyclerView recyclerView;

    private RecyclerView.ViewHolder currentViewHolder;
    private int currentViewType;

    RetrieveHeaderView(RecyclerView recyclerView) {
        this.recyclerView = recyclerView;
        this.currentViewType = DEFAULT_VIEW_TYPE;
    }

    RecyclerView.ViewHolder getViewHolderForPosition(int position) {
        if (currentViewType != recyclerView.getAdapter().getItemViewType(position)) {
            currentViewType = recyclerView.getAdapter().getItemViewType(position);
            currentViewHolder = recyclerView.getAdapter().createViewHolder(
                    (ViewGroup) recyclerView.getParent(), currentViewType);
        }
        //set top margin for sticky header to 0 as in message_header.xml it is present which is only required when header is in between of messages
        CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) currentViewHolder.itemView.getLayoutParams();
        layoutParams.setMargins(0, ZulipApp.get().getZulipActivity().getFloatingHeaderTopMargin(), 0, 0);

        //set viewHolder in ZulipActivity
        //adjust it when message list get scrolled
        ZulipApp.get().getZulipActivity().setViewHolder(currentViewHolder);
        return currentViewHolder;
    }
}