Fragments when defined in XML aren't actually views. The full view name is specified, or it assumes android.view
for the package and finds the rest. But a fragment is only truly specified when it includes the android:name
tag. It acts like a keyword, which are typically written in lower case. Thus, Fragment
refers to the class, and fragment
is the placeholder in XML for fragments.
As Andrew mentioned in the comments, any special item, such as <include>
and <merge>
are written in lower case, as they are not android.view
's.