问在RecyclerView滚动中隐藏FloatingActionButton

EN

<android.support.design.widget.CoordinatorLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <android.support.v7.widget.RecyclerView
                android:id="@+id/recyclerview_eventlist"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/fab_createevent"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/fab_margin"
                app:layout_anchor="@id/recyclerview_eventlist"
                app:layout_anchorGravity="bottom|right|end"
                app:layout_behavior="com.eventizon.behavior.ScrollAwareFABBehavior"
                android:src="@drawable/ic_edit"
                app:backgroundTint="@color/custom_color_1"
                app:borderWidth="0dp" />
        </android.support.design.widget.CoordinatorLayout>

    public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {


    private static final String TAG = "ScrollAwareFABBehavior";

    public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
        super();
        Log.e(TAG,"ScrollAwareFABBehavior");
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout,
            FloatingActionButton child, View target, int dxConsumed,
            int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        // TODO Auto-generated method stub
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed,
                dxUnconsumed, dyUnconsumed);
        Log.e(TAG,"onNestedScroll called");
        if (dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
            Log.e(TAG,"child.hide()");
            child.hide();
        } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
            Log.e(TAG,"child.show()");
            child.show();
        }
    }
}