Android layout syntax required

Question

here is the line in the layout file

<TextView android:id="@+id/username" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="@string/username" android:textAppearance="?android:attr/textAppearanceMedium" > 

in the context of what is the exact meaning

 android:textAppearance="?android:attr/textAppearanceMedium" 

is it related to "? [package:] [type:] name" , if so, what does it mean?

Answer 1

? android: attr / textAppearanceMedium refers to android.R.attr.textAppearanceMedium. This is a way to reference the contents of the resources of an external package.

The article is mentioned here.