Fling behavior for appbar and recyclerview

FlingBehavior

package ir.abrishamapp.abrishamandroidapp.Activities.OrdersLayer.DetailsViewer;

import android.content.Context;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

/**
 * Created by afshinhoseini on 9/14/16.
 */
public final class FlingBehavior extends AppBarLayout.Behavior {
    private static final int TOP_CHILD_FLING_THRESHOLD = 0;
    private boolean isPositive;
    private int verticalOffset = 0;

    public FlingBehavior() {
    }

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

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, AppBarLayout child, View dependency) {

        child.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {

                FlingBehavior.this.verticalOffset = verticalOffset;
                Log.e("Vertical offset", verticalOffset + "");
            }
        });

        return super.layoutDependsOn(parent, child, dependency);
    }

    @Override
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
        if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
            velocityY = velocityY * -1;
        }
        if (target instanceof RecyclerView && velocityY != 0) {
            final RecyclerView recyclerView = (RecyclerView) target;
            final View firstChild = recyclerView.getChildAt(0);
            final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
            consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;

        }

        Log.e("onNestedFling","Consumed");

        return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
    }

    @Override
    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY) {
        super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);

        if(target instanceof RecyclerView) {

            if(isPositive && verticalOffset > -child.getTotalScrollRange()) { // UP

                onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, true);
                return true;
            }
            else if(!isPositive) { // DOWN

            }
        }

        return false;
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
        isPositive = dy > 0;
    }
}