I added the android-support-library-v7-appcompat to my project to support ActionBar from API level 7 above.
It works like a charm on android 4.0+ an
Another alternative if you do not want to modify the source code of android-support-library-v7-appcompat is to add an empty layout in the layout xml file such as:
and make the fragment call to add to that layout instead:
ft.add(R.id.content_view, mFragment, mTag);