title: Custom item in the BottomNavigationView
body: <p>I would like to create a BottomNavigationView with menu with one custom layout item, but this custom layout is not visible in application. </p>
  
  <p>This is the menu:</p>
  
  <pre><code>&lt;menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"&gt;
  
      &lt;item
          android:id="@+id/menu_shopping"
          android:icon="@drawable/ic_tab_list"
          android:title="@string/shopping" /&gt;
  
      &lt;item
          android:id="@+id/menu_measurement"
          android:icon="@drawable/ic_tab_measure"
          android:title="@string/measurement" /&gt;
  
      &lt;item
          android:id="@+id/menu_notifications"
          android:title="@string/notifications"
          app:actionLayout="@layout/item_action_notification" /&gt;
  
      &lt;item
          android:id="@+id/menu_more"
          android:icon="@drawable/ic_tab_more"
          android:title="@string/more" /&gt;
  
  &lt;/menu&gt;
  </code></pre>
  
  <p>This is my custom layout:</p>
  
  <pre><code>&lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="45dp"
      android:layout_height="50dp"
      android:background="@drawable/ic_tab_notifications"&gt;
  
      &lt;RelativeLayout
          android:layout_width="22dp"
          android:layout_height="22dp"
          android:background="@drawable/red_circle"
          android:foregroundGravity="center"&gt;
  
          &lt;TextView
              android:id="@+id/notification_count"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_centerInParent="true"
              android:text="0"
              android:textColor="@color/white"
              android:textSize="10sp" /&gt;
  
      &lt;/RelativeLayout&gt;
  
  &lt;/FrameLayout&gt; 
  </code></pre>
  
  <p>This is activity layout: </p>
  
  <pre><code>&lt;android.support.design.widget.BottomNavigationView
      android:id="@+id/navigation_view"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      app:itemTextColor="@color/colorPrimaryDark"
      app:menu="@menu/menu_main" /&gt;
  </code></pre>
  
  <p>Any ideas? Thanks!</p>