Adding a notification badge to a ActionBarSherlock

I've already got this working, except that the notifications don't update. In other words, it's a static notification right now, and I want to make it dynamic.

I followed this java code: http://stackoverflow.com/a/17972602

My code is below:

Custom item in menu - Main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/badge"
        android:actionLayout="@layout/feed_update_count"
        android:showAsAction="always"
        android:title="Recent Alerts"
        android:orderInCategory="9999" />
</menu>

Custom shape drawable - shape_notification.xml

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" >
        <shape>
            <stroke 
                android:color="#22000000" 
                android:width="2dp"/>
            <corners 
                android:radius="5dp" />
            <solid 
                android:color="#ef4444"/>
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>
    <item>
        <shape>
            <stroke 
                android:color="#22000000" 
                android:width="2dp"/>
            <corners 
                android:radius="5dp" />
            <solid 
                android:color="#CC0001"/>
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>
</selector>

Layout for my view - feed_update_notification.axml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingRight="10dp"
    android:paddingLeft="10dp">
    <Button 
        android:id="@+id/notif_count"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minWidth="32dp"
        android:minHeight="32dp"
        android:background="@drawable/shape_notification"
        android:textSize="16sp"
        android:textColor="@android:color/white"
        android:gravity="center"
        android:padding="2dp"
        android:singleLine="true">
    </Button>
</RelativeLayout>

MainActivity - setting up (and attempting to update) my view

public static Button notifCount;
public static int mNotifCount = 0;

public override bool OnCreateOptionsMenu(IMenu menu) {
    SupportMenuInflater.Inflate(Resource.Menu.Main, menu);

    var count = menu.FindItem(Resource.Id.badge).ActionView;
    notifCount = (Button)count.FindViewById<Button>(Resource.Id.notif_count);
    notifCount.Text = mNotifCount.ToString();

    return base.OnCreateOptionsMenu(menu);
}

public void setNotifCount(int count) {
    mNotifCount = count;
    SupportInvalidateOptionsMenu();
}