Don't collapse Toolbar when RecyclerView fits

Question

I've made an app using Android Design Library, with a Toolbar and TabLayout.
Actually 2 tabs are present, both with 2 RecyclerView, that automatically collapse the Toolbar when scrolled.

My question is: can I disable Toolbar collapsing when RecyclerView has few items and completely fits the screen (like in TAB 2)?

I've seen a lot of examples like CheeseSquare, made by a Google employee where the issue is still present: even if the RecyclerView has just 1 item, the toolbar keeps hiding on scroll.

I think I can just find out if the first item of the RecyclerView is visible on screen and if yes disable toolbar collapsing. The former is easy to implement, what about the latter?

This is my layout:

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/coordinator_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_scrollFlags="scroll|enterAlwaysCollapsed"
            android:background="?attr/colorPrimary"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

        <android.support.design.widget.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/glucosio_pink"
            app:tabSelectedTextColor="@android:color/white"
            app:tabIndicatorColor="@color/glucosio_accent"
            app:tabTextColor="#80ffffff"/>
        </android.support.design.widget.AppBarLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/main_fab"
        android:layout_margin="16dp"
        android:onClick="onFabClicked"
        app:backgroundTint="@color/glucosio_accent"
        android:src="@drawable/ic_add_black_24dp"
        android:layout_gravity="bottom|right"
        />
    </android.support.design.widget.CoordinatorLayout>

Answer 1

You can check if the last item in RecyclerView is visible. If it's not then turn off scrolling programmatically using this method:

            //turn off scrolling
            AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
            toolbarLayoutParams.setScrollFlags(0);
            mToolbar.setLayoutParams(toolbarLayoutParams);

            CoordinatorLayout.LayoutParams appBarLayoutParams = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
            appBarLayoutParams.setBehavior(null);
            appBarLayout.setLayoutParams(appBarLayoutParams);

Answer 2

//turn off scrolling
AppBarLayout.LayoutParams toolbarLayoutParams = (AppBarLayout.LayoutParams) mToolbar.getLayoutParams();
toolbarLayoutParams.setScrollFlags(0);
mToolbar.setLayoutParams(toolbarLayoutParams);