结果是,当我向下滚动时FAB隐藏,但是当向上滚动时它不会再次出现:(类ScrollAwareFABBehavior与教程相同.但我使用的是嵌套布局.

这是我的布局(recyclerview位于content_main的LinearLayout中)：

<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="org.myorganisation.mypackage.someActivity">

    <include layout="@layout/toolbar" />

    <include layout="@layout/content_main" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/add_fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@drawable/plus"
        app:layout_behavior="org.myorganisation.mypackage.someActivity.helpers.ScrollAwareFABBehavior" />

    <LinearLayout
        android:id="@+id/insert_alert"
        android:layout_width="wrap_content"
        android:layout_height="50sp"
        android:layout_margin="@dimen/fab_margin"
        android:gravity="center_vertical"
        android:orientation="horizontal"
        android:paddingEnd="70sp"
        android:visibility="gone"
        app:layout_anchor="@id/add_fab"
        app:layout_anchorGravity="bottom|left">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            android:text="@string/initial_alert"
            android:textColor="@color/colorPrimaryDark"
            android:textStyle="bold|italic" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/ic_keyboard_arrow_right_black_24sp"
            android:tint="@color/colorPrimary" />
    </LinearLayout>

</android.support.design.widget.CoordinatorLayout>