CollapsingToolbarLayout causes RecyclerView’s bottom to be underscreen Code Answer

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.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:ignore="MergeRootFrame">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="@dimen/app_bar_height"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <!-- Problem HERE in app:layout_scrollFlags -->
        <com.google.android.material.appbar.CollapsingToolbarLayout
            android:id="@+id/toolbar_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:expandedTitleGravity="bottom"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed|snap" 
            app:toolbarId="@+id/toolbar">

            <TextView
                android:text="Hello, Hello, Hello, Hello, Hello, Hello, Hello, Hello, Hello, Hello"
                android:textSize="19sp"
                android:textStyle="bold"
                android:id="@+id/txtDescr"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:layout_collapseMode="parallax"
                app:layout_collapseParallaxMultiplier="0.5"/>

            <androidx.appcompat.widget.Toolbar
                android:id="@+id/detail_toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

            <com.google.android.material.floatingactionbutton.FloatingActionButton
                android:id="@+id/fab"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical|start"
                android:layout_margin="@dimen/fab_margin"
                app:layout_collapseMode="pin"
                app:srcCompat="@android:drawable/stat_notify_chat" />

        </com.google.android.material.appbar.CollapsingToolbarLayout>

    </com.google.android.material.appbar.AppBarLayout>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:scrollbars="vertical"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:scrollbarThumbVertical="@android:color/darker_gray"
        android:scrollbarSize="7dp"
        android:layout_height="match_parent"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

        private boolean hasFixedLastItemNotVisible = false;

        @Override
        public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);

            if (!hasFixedLastItemNotVisible &&
                    !recyclerView.canScrollVertically(10) &&
                    newState==RecyclerView.SCROLL_STATE_IDLE) {
                hasFixedLastItemNotVisible = true;
                recyclerView.getAdapter().notifyDataSetChanged();
            }
        }
    });