Xamarin Forms custom navigationbar

Hi, when I create a custom navigation bar in xamarin.android axml, the title remains empty, and I would like to know how can I set the textview title to that from xamarin.forms xml's title?
here is the custom navigationbar:
<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#FFFFFF"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
android:popupTheme="@style/ThemeOverlay.AppCompat.Light" >

</android.support.v7.widget.Toolbar>