The specific reason for this is that it provides @Null and @NotNull
annotations which should increase the safety of our code. Many of the
bugs which get filed are due to NullPointerExceptions, which could be
avoided by tooling using these annotations. The goal is to statically
catch this specific class of errors in as many situations as possible,
rather than waiting for them to occur at runtime.
Although Google is encouraging people to make old devices run apps
with the action bar (via appcompat-v7), they haven't provided a way
for people to create preference/setting screens with an action bar.
There are plenty of issues in the Android issue tracker relating
to this, but it doesn't yet seem to be on the radar of the Android
devs.
Until there is a native implementation of PreferenceFragment in
the appcompat-v7 support library, this submodule provides is a 3rd
party solution. It is actually a fork of the first repo in github,
though that was a bit of an upload and dump, without accepting MR's.
This fork includes gradle support.
