Navigation component fragment label is not working for with attribute string

Question

The fragment is in a module, So I made an attribute. The fragment is just showing that string attribute

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

   <TextView
       app:layout_constraintTop_toTopOf="parent"
       android:text="?attr/app_name"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
</androidx.constraintlayout.widget.ConstraintLayout>

My Fragment,

class TestFragment: Fragment(R.layout.fragment_test)

The attribute is in the module

   <attr name="app_name" format="string|reference"/>

?attr/app_name perfectly shows the value. However, when I use the same attribute in the navigation label, it shows some sort of number. My navigation graph is ,

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_graph"
    app:startDestination="@id/testFragment">

    <fragment
        android:id="@+id/testFragment"
        android:name="com.example.TestFragment"
        android:label="?attr/app_name" />
</navigation>

Does it work in navigation component? Thanks in advance.

Answer 1

Create string.xml in your module, then use android:label="@string/app_name"

Answer 2

Hope not too late but I think correct format is <attr name="title" format="string"/>