Modern Android Projects

Dependency injection

Events

Testing

About me

Java EE - 8 years

Android - 2 years

Did some Java desktop, Javascript, PHP, Databases, iOS along the way

Currently Development Manager of Spredfast Mobile (iOS and Android)

Pet projects (github.com/denisk20)

http://programmer-dvorak.appspot.com

Bullshit Bingo Champion Android app

Agenda

Dependency Injection
- Dagger

Events
- Otto event bus

Testing
- Unit tests
- Espresso

https://github.com/denisk20/di-events-testing-demo

Demo project

Dependency Injection

#1

What is D.I. ?

Dependency injection means giving an object its instance variables. Really. That's it.

James Shore, 22 March 2006

class WeatherActivity {
    
    WeatherManager weatherManager;

    @Override
    protected void onCreate() {
        weatherManager = new WeatherManager();

        WeatherNetClient netClient = new WeatherNetClient();
        netClient.setRequestQueue(new RequestQueue());
        weatherManager.setNetClient(netClient);
    }

    public void refreshWeather() {
        weatherManager.fetchWeather();
    }

}

public class WeatherActivity {

    @Inject WeatherManager weatherManager;

    protected onCreate() {
        ObjectGraph.create(new WeatherActivityModule())
            .inject(this);
    }

    public void refreshWeather() {
        weatherManager.fetchWeather();
    }

}

@Module
class WeatherActivityModule {

    @Provides RequestQueue provideRequestQueue() {
        return new RequestQueue();
    }

    @Provides WeatherNetClient provideWeatherNetClient(RequestQueue queue) {
        return new WeatherNetClient(queue);
    }

    @Provides WeatherManager provideWeatherManager(WeatherNetClient weatherNetClient) {
        return new WeatherManager(weatherNetClient);
    }

}

Google says:

Avoid dependency injection frameworks

https://developer.android.com/training/articles/memory.html#DependencyInjection

Dagger

Uses code generation (almost no reflection)
Optimized for Android

http://square.github.io/dagger/

Show me how you do it!

Android Dependency Injection summary

Is good when right tools are used

But wait, there's more...

Dagger 2

by Google

@Component(modules = DripCoffeeModule.class)
@Singleton
interface CoffeeShop {
  CoffeeMaker maker();
}

Faster
Generates code that looks hand-written
Uses zero reflection => no ProGuard configs
Module inheritance and many more...

Dagger http://square.github.io/dagger/

(intro talk by Jesse Wilson, Square

http://www.infoq.com/presentations/Dagger)

Dagger 2 http://google.github.io/dagger/

(intro talk by Gregory Kick, Google

https://www.youtube.com/watch?v=oK_XtfXPkqw)

Some links

Events

#2

Better code structuring
Asynchronous calls
Help to avoid inner classes

Events are great because:

class WeatherActivity {

    WeatherManager weatherManager;

    /**
     * Updates the weather for the first city from the list
     */
    void updateWeather() {
        weatherManager.fetchCities(new CitiesCallback() {
            @Override
            public void citiesUpdated(List<City> cities) {
                weatherManager.updateWeatherForCity(cities.get(0), new WeatherCallback() {
                    @Override
                    public void weatherUpdated(Weather weather) {
                        //do something with the weather here
                    }
                });
            }
    });
}

class WeatherActivity {
    WeatherManager weatherManager;

    public void updateCities() {
        weatherManager.fetchCities();
    }

    /**
     * Is called whenever cities list is updated by ANYONE
     */
    @Subscribe
    public void citiesUpdated(CitiesUpdatedEvent event) {
       weatherManager.updateWeatherForCity(event.getCities().get(0));
    }

    /**
     * Is called whenever ANY city is updated
     */
    @Subscribe
    public void cityUpdated(CityUpdatedEvent event) {
        City city = event.getCity();
        Weather weather = event.getWeather();
        //do something
    }
}

class WeatherActivity {

    WeatherManager weatherManager;

    TextView wind;

    void updateWeather() {
        weatherManager.updateWeather(new WeatherUpdatedCallback() {
            @Override
            public void weatherUpdated(Weather weather) {
                wind.setText(weather.getWind());
            }
        });
    }
}

class WeatherActivity {

    WeatherManager weatherManager;    //should be application-scoped

    TextView wind;

    void updateWeather() {
        weatherManager.updateWeather();
    }

    @Subscribe
    void weatherUpdated(WeatherEvent event) {
        wind.setText(event.getWeather().getWind());
    }
}

Otto Event Bus to the resque!

by Square

Dead simple
Fast
(as any Square library) Optimized for Android

Bus bus = new Bus();

bus.register(this);

bus.post(new MyEvent(myData));

@Subscribe
public void onMyEvent(MyEvent event) {
    //do something with event
}

bus.unregister(this);