Always use v4 Fragments instead of the build-in android.app.Fragment?

Question

I came across the ViewPager and the related FragmentPagerAdaptor which are not part of the regular Android packages, but only available in the V4 support package. It seems I cannot use the FragmentPagerAdaptor with a android.app.Fragment since the FragmentPagerAdaptor requires a v4 FragmentManager to instantiate. Reading Difference between Activity and FragmentActivity this seems to be aligned - use either v4 Fragments and related classes or the regular android.app.Fragments. Never mix.

Taking it further, I see no need to use the regular android.app.Fragments at all since they are less powerful than the v4 support packages. (Cite from another question: The Android Support package is not only for backports of newer APIs. It is also for other classes that, for whatever reason, are not being added to the SDK, such as ViewPager and its supporting classes.). The "only" downside I can think off is that the v4 support libraries is bundled with the APK which means my app will take up more space.

Am I correct to conclude that I should always use v4 support libraries for fragments since those include more functionality? (And they are backwards compatible, not to forget.)

Answer 1

I just realized that it is possible to use the android.app.Fragment and the android.support.v4.view.ViewPager together... If you use the android.support.v13.app.FragmentPagerAdapter... So it seems that the v13 support package solves/improves the compatibility issues between android.app.Fragment and android.support.v4.view.ViewPager. What a mess.

While this resolves the particular example I came up with, I am still wondering if the best option is to always use v4 classes when they are available instead of the build-in classes (e.g. android.app.Fragment) even if I am only worried about ICS and newer devices?