Android free/paid - architecture using library

Question

I need to create a free and paid version of the app and therefore I am using a library project with the common activities and resources in. However I was wondering how you would go about organising this:

A shared (library) activity MyActivity.java launches a DialogFragment when a user clicks a buttons. The DialogFragment will be different for the free and paid apps. For the free app we will launch FreeDialog.java and for paid we will launch PaidDialog.java. These two dialog fragments will not be in the library project as they are not shared; they will be in the free and paid projects separately.

The only thing I can think is to make MyActivity.java abstract and to extend it in the free and paid projects. The extensions will launch their respective DialogFragments.

Another way could be to overload the Fragments in each of the projects. However, I am not sure if this is possible.

Answer 1

Theoretically, you could make MyActivity abstract, and subclass it in both paid and free app projects. But, Activity classes are a little different than normal Java classes, which complicates this. They are listed in AndroidManifest.xml, and then also are not created by simply newing them up. They're normally created with Intents. So, I think I would stay away from making the Activity an abstract class.

I think what you really want is to use is something like the Factory pattern to create an instance of DialogFragment, where your common library does not know which DialogFragment will be created. You can get pretty fancy with a factory, and you can read all about that elsewhere, but a simple one might work for you:

public class FragmentFactory {

   private static String _dialogFragmentClassName;

   public static void registerFragment(String className) {
      // you might choose to assert if _dialogFragmentClassName != null
      _dialogFragmentClassName = className;
   }

   public static DialogFragment createFragment() {
      try {
         return (DialogFragment) Class.forName(_dialogFragmentClassName).newInstance();
      } catch (Exception e) {
         return null;
      }
   }
}

Then, in your free and paid app project code, you would issue calls like this at startup (e.g. in a main Activity):

FragmentFactory.registerFragment(com.mycompany.free.FreeDialogFragment.class.getName());

and

FragmentFactory.registerFragment(com.mycompany.paid.PaidDialogFragment.class.getName());

Finally, in the common library code, you can create an instance of the fragment by calling

DialogFragment fragment = FragmentFactory.createFragment();
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.fragment_content, fragment);
ft.commit();