Quero adicionar o spinner como um item na minha gaveta de navegação. Onde devo colocar o botão rotativo como um item? Onde inflar o layout do spinner? Onde inicializar o spinner? Eu quero que fique assim:

É aqui que adiciono meus itens:

<menu xmlns:android="http://schemas.android.com/apk/res/android">

<group
    android:id="@+id/group1"
    android:checkableBehavior="single">
    <item
        android:id="@+id/nav_login"
        android:icon="@drawable/ic_login"
        android:title="@string/login_menu_item"/>
    <item
        android:id="@+id/nav_signup"
        android:icon="@drawable/ic_signup"
        android:title="@string/signup_menu_item"/>
    </group>

<item android:title="@string/language">
    <menu>
        <item
            android:id="@+id/nav_eng"
            android:title="@string/english">
        </item>

        <item
            android:id="@+id/nav_heb"
            android:title="@string/hebrew">
        </item>
    </menu>

Este é o meu layout com a gaveta:

<LinearLayout 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"
          android:orientation="vertical">

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toolbar_home"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorPrimary"
    android:minHeight="?attr/actionBarSize"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
    app:title="Masü"
    />

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:openDrawer="start">

    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:itemIconTint="@color/colorAccent"
        app:itemTextColor="@color/textColorSecondary"
        app:menu="@menu/activity_home_drawer"/>
</android.support.v4.widget.DrawerLayout>
</LinearLayout>

E no clique de um item, é assim que funciona:

public boolean onNavigationItemSelected(MenuItem item) {
    int id = item.getItemId();
    mDrawerLayout.closeDrawers();

    if (id == R.id.nav_login) {
        if (mIsLoggedin) {
            logout();
        } else {
            mFragmentTransaction = mFragmentManager.beginTransaction();
            mFragmentTransaction.replace(R.id.fragment_container, new LoginFragment()).commit();
        }