New Android Project: The Most Important Decisions - Vasiliy Zukanov
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Vasiliy Zukanov discusses important architectural decisions for a new Android project. He recommends adopting dependency injection from the start using Dagger to reduce coupling and improve testability. He also advocates decoupling UI logic from views using an MVx pattern like MVVM to make the code more maintainable and testable. Finally, he suggests initially organizing code into features packages rather than screens to better reflect the business domain.
New Android Project: The Most Important Decisions - Vasiliy Zukanov
- 1. New AndroidProject: TheMost ImportantDecisions Vasiliy Zukanov FreelanceAndroid developer & consultant Twitter: VasiliyZukanov Blog: TechYourChance.com
- 2. Whostarted a new professional Android project in the past 3years? …past2 years? …pastyear? @VasiliyZukanov 2
- 3. Which language, frameworks, libraries,practices,etc. should Iuse in a new project? @VasiliyZukanov 3 RxJava Kotlin Java Coroutines ViewModel Koin Dagger Navigation Conductor MVI MVVM MVP MVC AutoValue ConstraintLayout Timber ThreadPool LiveData Glide Fragment Single-activity WorkManager EventBus Gson Picasso Fresco Coil SqlDelight Room Moshi Firebase Flow Modularization
- 5. “Architecture represents the significant design decisions that shape asystem, where significantis measured by cost of change. @VasiliyZukanov 5 Architecture – GradyBooch
- 6. “Architecture is the set of decisions that are hard to change. @VasiliyZukanov 6 Architecture – Martin Fowler
- 7. Architecture ≈ Subset of design decisions that affect the cost ofchange the most ≈ Maintainability! @VasiliyZukanov 7
- 8. Maintainability isimportant Aswell asstaying pragmatic and getting stuff done! @VasiliyZukanov 8
- 9. ThePareto principle (80-20rule) 80%of the effects come from 20%of thecauses @VasiliyZukanov 9
- 11. Dependencyinjection misconception public class SomeClient { private f i n a l SomeService mSomeService; public SomeClient() { mSomeService = new SomeService(); } } public class SomeClient { private f i n a l SomeService mSomeService; public SomeClient(SomeService someService) { mSomeService = someService; } } That’s bad becauseUNITTESTS! (can’t replace the implementation) That’s good becauseUNITTESTS (can replace the implementation) @VasiliyZukanov 11 So, no need for DIif you don’t unit test and neverreplaceimplementations?
- 12. Reusechallenge @VasiliyZukanov 12 public class FetchCurrentUserUseCaseSync { public FetchCurrentUserUseCaseSync(ParseUserConverter parseUserConverter, ParseUsersRetriever parseUsersRetriever, OfflineDetector offlineDetector, MyLogger myLogger) { . . . } @WorkerThread public CurrentUser fetchCurrentUser() { . . . } } Toget current user’s info Ineed: this client +4 services +3 transitive services =instantiate 8 objects FetchCurrentUserUseCaseSyncis used in 14 different places!
- 13. Reusestrategies @VasiliyZukanov 13 Manually instantiate 8 * 14 =112 objects Reduceobjects count through code duplication(multiplication) God Objects Static calls and global static state (e.g.Singletons) Dependency injection Pretty much guaranteed if you don’t useDI
- 14. DependencyInjection Architectural Pattern Applica tio n Construc t ion Set class Functional Set class integration @VasiliyZukanov 14 Instantiation logic for eachservice is definedonce in constructionset, and thenall classes from functional set simplyget the required dependencies from outside
- 15. DependencyInjection example public class ClipSettingsFragment extends BaseFragment { @Inject ViewMvcFactory mViewMvcFactory; @Inject ClipSettingsController mController; @Override public void onCreate(@Nullable Bundle savedInstanceState) { getControllerComponent().inject(this); super.onCreate(savedInstanceState); } @Nul l a b le @Overri d e public View onCreateView(@NonNull LayoutInflater i n f l a t e r, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { . . . } . . . } Declare the requiredservices Delegate resolution to Dagger @VasiliyZukanov 15 Reusedtens of transitive dependencies; thousands of lines ofcode
- 16. Dependency Injection is very beneficial, but extremelyhard to introduce into existingcode @VasiliyZukanov 16 Adopt it from the onset of your new project!
- 17. Dagger dependency injection framework is the bestchoice for most Android projectstoday @VasiliyZukanov 17
- 19. Define application’s UI Capture user’s interactions with theUI @VasiliyZukanov 19 UI logic responsibilities
- 20. Why decouple UI logicspecifically? @VasiliyZukanov 20
- 21. Detailed and accurate requirements (UImockups) Much higher rate of change in most cases Unreadable - verbose, messy,hacky,etc. Easiest to test manually Hardest to testautomatically @VasiliyZukanov 21 UI logic characteristics
- 22. Decoupling of UI logic is the main rationalebehind MVx presentation layer architecturalpatterns @VasiliyZukanov 22
- 23. Kotlin Multiplatform?Jetpack Compose? Example of decoupledUI @VasiliyZukanov 23
- 24. More information about UI decoupling and MVx in my talk from Droidcon Berlin2018 @VasiliyZukanov 24
- 25. Adopt some MVx at the beginning of a new project Youcanchangeyour mind later* @VasiliyZukanov 25
- 26. Package byfeature @VasiliyZukanov 26 Top-level packagesshould correspond to core concepts of app’sbusinessdomain
- 27. Package by featureexamples Google IO2019 app @VasiliyZukanov 27
- 28. Feature ≠screen Clip playback screen Settings screen Standalone domain features prevent inter-dependenciesbetween unrelated screens @VasiliyZukanov 28 Looks like asingle “clips” feature… …but…
- 29. Avoid preliminarymodularization Feature packages are straightforward to extractas feature modules IFand WHENthe need will arise @VasiliyZukanov 29
- 30. As you add more features, you learn more about your business domain @VasiliyZukanov 30 Constantly refactor feature packagestoreflect your most up-to-date understanding
- 31. Dependency Injection, MVx and Package-by-Feature willgive you the “80% of architecture” on mostprojects @VasiliyZukanov 31
- 32. Use the tools you’re familiarwith @VasiliyZukanov 32
- 34. My Android Development Courses www.TechYourChance.com @VasiliyZukanov 34
- 36. References @VasiliyZukanov 36 1. Making Architecture Matter (Martin Fowler) -https://youtu.be/DngAZyWMGR0 2. Dependency Injection in Android - https://www.techyourchance.com/dependency-injection- android/ 3. Activities and Fragments are not MVx Views (Vasiliy Zukanov)- https://youtu.be/oOARoQr4H5U