A simple RecyclerView where a Quick Return view can be added either at the top or the bottom. Inspired by https://github.com/LarsWerkman/QuickReturnListView

fragment_recyclerview.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <com.example.ui.widgets.QuickReturnRecyclerView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="0dp" />

    <android.support.v7.widget.Toolbar
        android:id="@+id/BottomToolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="#f2ffffff"
        android:minHeight="?attr/actionBarSize"" />

</FrameLayout>

QuickReturnRecyclerView.java

import android.content.Context;
import android.os.Build;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.TranslateAnimation;
import android.widget.FrameLayout;

/**
 * Add view with BottomToolBarRecyclerView.setReturningView to be used as a QuickReturnView
 * when the user scrolls down the content.
 *
 * Created by johnen on 14-11-11.
 */
public class QuickReturnRecyclerView extends RecyclerView {
    private static final String TAG = QuickReturnRecyclerView.class.getName();

    private View mReturningView;
    private static final int STATE_ONSCREEN = 0;
    private static final int STATE_OFFSCREEN = 1;
    private static final int STATE_RETURNING = 2;
    private int mState = STATE_ONSCREEN;
    private int mMinRawY = 0;
    private int mReturningViewHeight;
    private int mGravity = Gravity.BOTTOM;

    public QuickReturnRecyclerView(Context context) {
        super(context);
        init();
    }

    public QuickReturnRecyclerView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public QuickReturnRecyclerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init(){
    }

    /**
     * The view that should be showed/hidden when scrolling the content.
     * Make sure to set the gravity on the this view to either Gravity.Bottom or
     * Gravity.TOP and to put it preferable in a FrameLayout.
     * @param view Any kind of view
     */
    public void setReturningView(View view) {
        mReturningView = view;

        try {
            FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) mReturningView.getLayoutParams();
            mGravity = params.gravity;
        } catch (ClassCastException e) {
            throw new RuntimeException("The return view need to be put in a FrameLayout");
        }

        measureView(mReturningView);
        mReturningViewHeight = mReturningView.getMeasuredHeight();
        setOnScrollListener(new RecyclerScrollListener());
    }

    private void measureView(View child) {
        ViewGroup.LayoutParams p = child.getLayoutParams();
        if (p == null) {
            p = new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.FILL_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT);
        }

        int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0, p.width);
        int lpHeight = p.height;
        int childHeightSpec;
        if (lpHeight > 0) {
            childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);
        } else {
            childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
        }
        child.measure(childWidthSpec, childHeightSpec);
    }

    private class RecyclerScrollListener extends OnScrollListener {
        private int mScrolledY;

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            if(mGravity == Gravity.BOTTOM)
                mScrolledY += dy;
            else if(mGravity == Gravity.TOP)
                mScrolledY -= dy;

            if(mReturningView == null)
                return;

            int translationY = 0;
            int rawY = mScrolledY;

            switch (mState) {
                case STATE_OFFSCREEN:
                    if(mGravity == Gravity.BOTTOM) {
                        if (rawY >= mMinRawY) {
                            mMinRawY = rawY;
                        } else {
                            mState = STATE_RETURNING;
                        }
                    } else if(mGravity == Gravity.TOP) {
                        if (rawY <= mMinRawY) {
                            mMinRawY = rawY;
                        } else {
                            mState = STATE_RETURNING;
                        }
                    }

                    translationY = rawY;
                    break;

                case STATE_ONSCREEN:
                    if(mGravity == Gravity.BOTTOM) {

                        if (rawY > mReturningViewHeight) {
                            mState = STATE_OFFSCREEN;
                            mMinRawY = rawY;
                        }
                    } else if(mGravity == Gravity.TOP) {

                        if (rawY < -mReturningViewHeight) {
                            mState = STATE_OFFSCREEN;
                            mMinRawY = rawY;
                        }
                    }
                    translationY = rawY;
                    break;

                case STATE_RETURNING:
                    if(mGravity == Gravity.BOTTOM) {
                        translationY = (rawY - mMinRawY) + mReturningViewHeight;

                        if (translationY < 0) {
                            translationY = 0;
                            mMinRawY = rawY + mReturningViewHeight;
                        }

                        if (rawY == 0) {
                            mState = STATE_ONSCREEN;
                            translationY = 0;
                        }

                        if (translationY > mReturningViewHeight) {
                            mState = STATE_OFFSCREEN;
                            mMinRawY = rawY;
                        }
                    } else if(mGravity == Gravity.TOP) {
                        translationY = (rawY + Math.abs(mMinRawY)) - mReturningViewHeight;

                        if (translationY > 0) {
                            translationY = 0;
                            mMinRawY = rawY - mReturningViewHeight;
                        }

                        if (rawY == 0) {
                            mState = STATE_ONSCREEN;
                            translationY = 0;
                        }

                        if (translationY < -mReturningViewHeight) {
                            mState = STATE_OFFSCREEN;
                            mMinRawY = rawY;
                        }
                    }
                    break;
            }

            /** this can be used if the build is below honeycomb **/
            if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.HONEYCOMB) {
                TranslateAnimation anim = new TranslateAnimation(0, 0, translationY, translationY);
                anim.setFillAfter(true);
                anim.setDuration(0);
                mReturningView.startAnimation(anim);
            } else {
                mReturningView.setTranslationY(translationY);
            }
        }
    }
}

Thanks for sharing your work.
This is a good adaptation but you missed something. You did not take over-scrolling into account.

Add this to onScrolled to fix that (It will stutter a bit for the top item, but it works flawlessly otherwise)

    @Override
            public void onScrolled(int dx, int dy) {
//initialise the instance variable shouldScroll as false in the constructor
       if(!shouldScroll){
                    shouldScroll=!(((LinearLayoutManager)getLayoutManager()).findLastCompletelyVisibleItemPosition()==(getAdapter().getItemCount()-1));
                }

                if((QuickReturnRecyclerView.super.computeVerticalScrollOffset()<1 && dy<0)||(!shouldScroll)){                    if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.HONEYCOMB) {
                    TranslateAnimation anim = new TranslateAnimation(0, 0, 0, 0);
                    anim.setFillAfter(true);
                    anim.setDuration(0);
                    mReturningView.startAnimation(anim);
                } else {
                    mReturningView.setTranslationY(0);
                }
                mScrolledY=0;
                mMinRawY=0;
                mState=STATE_ONSCREEN;
                return;
            }else{
                   // do the usual
            }

A classic discrepancy between code and comment:
Line 178 states "this can be used if the build is below honeycomb" but
line 179 states "SDK_INT <= HONEYCOMB" (less or EQUAL)

So, I guess < would be what you want??