How to hide Floating Action Button on Nested Scroll

Question

I'm trying to hide two FAB on Nested Scroll scrolling. I've tried to implement my own FAB behavior but it did't work. FAB's don't react on scrolling at all. Note: I deleted some part of layout to fit the post.

Layout

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="ru.berezin.maxim.im.budget_v3.userinterface.StartPage">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appcollapse"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/testingscroll"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="none"
        app:behavior_overlapTop="30dp"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <!--content including-->
        <include layout="@layout/start_content_layout"/>

    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/start_page_fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="16dp"
        android:src="@drawable/plus"
        app:layout_anchor="@id/testingscroll"
        app:layout_anchorGravity="end|bottom"
        app:layout_behavior="ru.berezin.maxim.im.budget_v3.FabOnScroll"
        />

    <View
        android:id="@+id/dummy"
        android:layout_width="1dp"
        android:layout_height="16dp"
        app:layout_anchor="@id/start_page_fab"
        app:layout_anchorGravity="top|right|end"
        />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/account_det_add_transfer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|top"
        android:layout_margin="16dp"
        android:src="@drawable/minus"
        app:layout_anchor="@id/dummy"
        app:layout_anchorGravity="top|right|end"
        app:layout_behavior="ru.berezin.maxim.im.budget_v3.FabOnScroll"
        />
</android.support.design.widget.CoordinatorLayout>

FabOnScroll class

public class FabOnScroll extends FloatingActionButton.Behavior {
        public FabOnScroll(Context context, AttributeSet attrs) {
            super();
        }

        @Override
        public void onNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
            super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);

            //child -> Floating Action Button
            if (dyConsumed > 0) {
                CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) child.getLayoutParams();
                int fab_bottomMargin = layoutParams.bottomMargin;
                child.animate().translationY(child.getHeight() + fab_bottomMargin).setInterpolator(new LinearInterpolator()).start();
            } else if (dyConsumed < 0) {
                child.animate().translationY(0).setInterpolator(new LinearInterpolator()).start();
            }
        }

        @Override
        public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View directTargetChild, View target, int nestedScrollAxes) {
            return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
        }

    }

Answer 1

So, I fixed it. Not exactly what I wanted, but it's working. I dont have any ideas why, but for some reason dyConsumed is always equals 0. But I noticed that dyUnconsumed is changing while I scroll. So I've just add dxUnconsumed check to my If/else statment and it's worked. Can someone explain why dyConsumed equals 0?