RxJava support

[zugaldia]

WIP to bring back support for Rx as part of the libjava-services-rx module.

The first stab at it, extending the current MapboxDirections class, works but brings an inconsistent API. Unlike with the normal client where the Builder brings the MapboxDirections instance. Right now, we need to use them separately as we cannot use the build method:

MapboxDirectionsRx.Builder builder = new MapboxDirectionsRx.Builder()
  .setAccessToken(Utils.getMapboxAccessToken(this))
  .setCoordinates(positions)
  .setProfile(DirectionsCriteria.PROFILE_DRIVING)
  .setSteps(true)
  .setOverview(DirectionsCriteria.OVERVIEW_FULL);
MapboxDirectionsRx clientRx = new MapboxDirectionsRx(builder);
clientRx.getObservable()
  .subscribeOn(Schedulers.newThread())
  .observeOn(AndroidSchedulers.mainThread())
  .subscribe(new Action1<DirectionsResponse>() {
    @Override
    public void call(DirectionsResponse response) {
      DirectionsRoute currentRoute = response.getRoutes().get(0);
      Log.d(LOG_TAG, "Response code: " + response.getCode());
      Log.d(LOG_TAG, "Distance: " + currentRoute.getDistance());
    }
  });

This needs one more iteration.

Fixes #131.

cc: @mapbox/android for folks familiar with Rx willing to get some 👀.

[zugaldia]

Alright, nothing that couldn't be fixed bringing some generics to the Builder class (f6fb9f9). Now the API for Rx looks similar the non-Rx one:

MapboxDirectionsRx clientRx = new MapboxDirectionsRx.Builder()
  .setAccessToken(Utils.getMapboxAccessToken(this))
  .setCoordinates(positions)
  .setProfile(DirectionsCriteria.PROFILE_DRIVING)
  .setSteps(true)
  .setOverview(DirectionsCriteria.OVERVIEW_FULL)
  .build();
clientRx.getObservable()
  .subscribeOn(Schedulers.newThread())
  .observeOn(AndroidSchedulers.mainThread())
  .subscribe(new Action1<DirectionsResponse>() {
    @Override
    public void call(DirectionsResponse response) {
      DirectionsRoute currentRoute = response.getRoutes().get(0);
      Log.d(LOG_TAG, "Response code: " + response.getCode());
      Log.d(LOG_TAG, "Distance: " + currentRoute.getDistance());
    }
  });

(Working sample in DirectionsV5Activity.)

If this looks good to @mapbox/android we just need to bring in some test and adapt the same approach to the other clients (distance, geocoding, mapmatching, staticimage).

[cammace]

Would it make sense to also have a libandroid-rx module for our geocoding widget and other future widgets/UI elements?

[zugaldia]

Would it make sense to also have a libandroid-rx module for our geocoding widget and other future widgets/UI elements?

Yes, but let's wait to have some content before we create the module. For example, #4 should closed for now as it's unclear that the benefits of the Rx approach in the widget outbalance the weight of the dependency.

@cammace PR is ready, care to review please?

[cammace]

👍