Android data binding - 'No resource identifier found for attribute'

You must use the data binding syntax. It should be:

<TextView
      android:text="@string/hello_world"
      android:layout_width="wrap_content"
      app:fontName='@{"Roboto-Regular.ttf"}'
      android:layout_height="wrap_content"/>

This same error can also happen if you forget the closing curly brace:

android:text="@{viewModel.foo"