Java – How useful is JNI in android

Android applications are fundamentally built around Model-View-Controller (MVC) - MVP sounds like the same thing, although I've not heard the term before. Activities fill the role of Controller, XML Views are just that (although you can build them programmatically in the Activity - it's just easier and simpler to do it in XML), and the Model you write yourself. So yes, that model is quite practical.

A possible reason you may not have heard much about this design model is that the Android framework forces you to separate the view out. Because the application on mobile devices tend to be small, people don't tend to use full-on MVC; they tend toward view and action layers where the action layer does much of the model's (small) job.

If you are writing a cross platform app, you may want to look at a four-layer approach: View, Action, Business Logic, and Model. The View and Action layers would be platform specific, while the Business Logic and Model would not change. Basically, you split out the presenter and user interaction out to the Action layer, which calls the Business Logic layer to perform the action the user wants.

The accepted pattern is to have a factory method inside your custom fragment class (typically called newInstance() but hey dealer's choice). So your fragment class should look something like this:

public class MyFragment extends Fragment
{
    public static MyFragment newInstance()
    {
        MyFragment newFragment = new MyFragment();
        // add any bundle arguments here if needed
        return newFragment;
    }
    // rest of fragment class...
}

Then, when you create a fragment and add it to the backstack, instead of saying:

MyFragment fragment = new MyFragment();

You can use the factory method instead of the 'new' keyword.