Android Architecture (Dagger 2)

Slides from my talk at Mobilatorium meetup

Transcript

1. Android Architecture How to build better Android apps with Dagger Alex Korovyansky Google Developer Expert
2. Dependency Injection • Software design pattern that implements inversion of control and allows a program design to follow the dependency inversion principle. The term was coined by Martin Fowler. • Separates behaviour of something from its required classes 2 Component Service
3. public class Component { private final Service service; public Component() { this.service = new ServiceImpl(); } public void doStuff() { return service.doStuff(); } } 3 ? public interface Service { public void doStuff(); }
4. 4 public class CatsService implements Service { @Override public void doStuff() { System.out.println("Cats are better than dogs!") } } public class DogsService implements Service { @Override public void doStuff() { System.out.println("Dogs are better than cats!") } }
5. public class Component { private final Service service; public Component() { this.service = new CatsService(); } public void doStuff() { return service.doStuff(); } } 5 ? public interface Service { public void doStuff(); }
6. Basic Idea 6 Component <<interface>> Service ServiceImpl Assembler <<create>>
7. Styles 7 • Constructor Injection • Setter Injection • Interface Injection
8. 8 public class Component { private final Service service; public Component(Service service) { this.service = service; } public void doStuff() { return service.doStuff(); } } ^^ Constructor Injection ^^
9. Frameworks • PicoContainer • Spring • Guice • Avalon • … 9
10. JSR-330 • @Inject • @Named • @Qualifier • @Scope • @Singelton 10
11. Advantages of DI • Loosely coupled programs • Following single responsibility principle • Easy to write tests / extend / maintain • Reduction of boilerplate code • Parallel development • … 11
12. What about Android? 12
13. Frameworks • PicoContainer • Spring • Guice • Avalon • … 13
14. Guice • Powerful, dynamic, well-tested, wide-spread, etc… • Canonical standard for dependency injection • Configuration problems fail at runtime • Slow initialization, slow injection, memory problems 14
15. Frameworks • PicoContainer • Spring • Guice • Avalon • … 15
16. Dependencies graph 16 Tweeter Twitter API HTTP Client User Manager Shared Preferences Account Manager
17. DAG-ger 17 Tweeter Twitter API HTTP Client User Manager Shared Preferences Account Manager
18. Dagger2 • The first to implement the full stack with generated code • @Module + @Provides: mechanism for providing dependencies • @Inject: mechanism for requesting dependencies • @Component: bridge between @Module and @Inject 18
19. Providing Dependencies • Modules are classes that provide dependencies • @Module annotation on the class • @Provider annotation on a method indicates that its return type is a dependency 19
20. Demo https://github.com/google/dagger 20
21. Q&A 
 Alex Korovyansky inbox@alexkorovyansky.com http://about.me/AlexKorovyansky 21