Modular android project - how?

Question

My scenario

I have to implement a "modular" android app. There is a core module from which I should be able to invoke other modules. Each module provides a different feature to the user. Imagine I am making a city guide, then one module may contain a map with POIs, another one an event calendar and a third one pre-defined city guides. The modules contain views to be loaded in activities of the core module (like dashboards where each module puts its item/picture). They also contain activities which should be invoked (like when a user taps an item on the dashboard). As far as I know, I will need a database and/or preferences only in the core module. The "plug-in modules" use classes (utilities) of the core module, e.g. when connecting to the backend.

My solution on iOS

For iOS, I achieved this with targets in XCode. I have one project and depending on the customer's needs I compile only the relevant modules. It would be even better if the user can install modules whenever he wants, without the need of reinstalling the "core" application.

My problems on Android

In SO, I already found various solutions like library project, switching from Eclipse to Android Studio + something, using package manager and broadcast receiver... But I still don't understand... How is the modularity of an android application to be achieved?

Here are some concrete problems that I see:

• Libraries: My modules all use classes of the core module, so they are not independent. I achieve the modularity by using interfaces/inheritance depending on the flexibility that I need.

• Broadcast receiver: This seems to be everything else than recommended. See, for example, here or here.

What I need is, at least, to be able to use the same code for delivering app with features A and B to one customer and with B and C to another one. And, until now, I have no idea how to achieve it.

PS: I don't want to use scripting, I am not familiar with that.

Answer 1

I don't see this "modular" app as anything different from one app, with several packages, each containing discrete functionality, that is adapted to some list of settings or external parameter (either provided by the user or you).

My approach would be to have a "main" package. That package would contain the shared functionality you mention above and serve as the hub for your application. I would then create separate sub-packages for the different "add on" functionality. This allows you to still use the code in your main package with a simple import statement. From your description these additional functions should probably be implemented as a Fragment. A Fragment is almost a stand alone application with the exception that it is "hosted" by an Activity. Depending on how these add on functions are used (I cannot tell if they relate to the UI, just background processing etc) you could easily have 3 of 4 different fragments and choose to load only 1 or 3 or 2 of them at runtime.

To control which parts of the code are used I would just set up a simple switching class (it could even be part of the first activity launched, I cant tell from your description above). Here I would check for some setting indicating which parts of the app will be "active." This could be easily defined using SharedPreferences to store a specific configuration, e.g. use A and B, prior to delivering the final project. You would then just initialize the fragments you need and display them either (1) individually in a Fragment layout element or FrameLayout; (2) collectively in some other view structure like a ViewPager.

I follows your links on the BroadcastReceiver and I am still not sure why they are "everything else than recommended." Used correctly a BroadcastReceiver is very useful. I tend to use a LocalBroadcastManager along with a BroadcastReceiver to notify other sections of the app when some AsyncTask, e.g. downloading a lot of data, is complete. These parts of the app can then access a local database or process the information downloaded on their own time. I wouldn't use a BroadcastReceiver to modulate parts of the app if that is what you're looking for. I would instead just use a SharedPreference file to set the configuration at runtime.

Answer 2

If you need modules like facebook sdk or something like that better use library project. If you use Idea or Android Studio there is such thing like Module. If I need some modeles in one app I prefer just put in different packages like com.appname.model, com.appname.ui and so on. Broadcast Receiver isn't about modules. As I know there isn't analog of ios target.