#MVP demo
A simple MVP demo.
Uses RXJava for network calls
Uses Dagger 2 for dependency injection
##PLEASE NOTE
The demo comes in two product flavours: "prod" and "mock".
To run the application please select the "prod" flavour.
To run the instrumented tests please select the "mock" flavour, it injects a mock api dependency.
##Technical considerations
###Tests
JUnit and Instrumented (Espresso) tests are present in the respective source folders.
Tests use Mockito for mocking, verifying and captors.
Coverage is 19% of classes, 10% of lines. More tests need to be written.
###Architectural approach
A simple implementation of the MPV pattern is applied.
The Presenters subscribe to the Model via Observers (RxAndroid) to receive the data. They subscribe in onResume() and unscubscribe in onPause() to avoid leaks. The requests to the api are cached using the Observable.cache() operator.
The requests are retried in case InterruptedIOException.
We need to store the cached requests themselves so that they survive config changes, otherwise there would be no benefit in caching.
I decided to use Singletons and inject them in the Model using Dagger.
I am aware this approach is debatable, other solutions are possible:
use a Service (started service to outlive the Activity config changes, bound to allow communication), use a retained Fragment, store
them in the Application. In any case Observable is not Serializable nor Parcelable therefore use Activity.onSaveInstanceState(Bundle) is not an option.
The app uses one Activity and two Fragments.
###Retry logic
Here we transform a series of Observables that emit a Throwable into one Observable (hence flattened) that emits a series of either onComplete() or onError().
Api.getAllFilms().retryWhen(exceptions -> exceptions.flatMap(exception -> {
if (exception instanceof InterruptedIOException) {
return Observable.just(null);
}
return Observable.error(exception);
}));
We retry only in case of InterruptedIOException.
retryWhen Javadoc: http://reactivex.io/RxJava/javadoc/rx/Observable.html#retryWhen(rx.functions.Func1)