title: Adding Fragments to the Activity's root view
body: <p>Is it safe to assume that an <code>Activity</code>'s root view will always be a <code>ViewGroup</code>? I have an <code>Activity</code> that displays various <code>Fragment</code>s. Can I skip creating a layout XML for the <code>Activity</code> and directly add <code>Fragment</code>s to its root view?</p>