The (best) good practices on android

After more than 5 years working on Android, I have found a set of common problems that Android teams run into. In this talk we will go through a list of tips & tricks that can help these teams to improve their code and raise the quality bar.

The best practices do not exist, but the good ones do, and you will go home knowing a ton of them.

Transcript

1. The Best Good Practices in Android Jorge Juan Barroso Carmona jorge@karumi.com @flipper83 +JorgeJBarroso Android Guy Android GDE
2. Basho. Poet Karumi is the beauty of ordinary things spoken of in a simple way.
3. Sergio Gutierrez Senior Mobile Engineer Pedro Gomez Senior Mobile Engineer Alberto Gragera Technical Director Davide Mendolia Senior Full Stack Engineer Fran Toro Senior Mobile Engineer
4. Adam Tornhill “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” Martin Fowler
5. Silver Bullets do NOT Exist.
6. Design Tips
7. Organize your styles and themes
8. Custom views and merge clean your layout.xml and help to readability and refactoring.
9. Code Tips
10. Segregate Layer Responsibilities
11. Choose well your Interfaces
12. Main thread is Sacred
13. Memory leak is not OutOfMemoryException. WeakReference is your friend.
14. The Truth Is In The Code! Android is open source
15. STUPID
16. Singleton Invasion STUPID
17. Adam Tornhill AllMyActivities.java If (UserDataManager.getInstance.hasUser(context)) { User user = UserDataManager.getInstance() .getUser(context, userId); /*...*/ } STUPID
18. Tight Coupling S TUPID
19. Adam Tornhill public class UserDataManager { private User getUser(Context context, String id) { Cursor<User> cursor = userContentProvider.getUser(context, id); if(cursor == null) { cursor = loadUserFromApi(id); } /*…*/ return user; } s TUPID
20. Untestability st UPID
21. Adam Tornhill long timeElapse = System.currentTimeMillis() - lastTime; st UPID
22. Premature Optimization Stu PID
23. Adam Tornhill String sessionId = sharedPreferences.getString(KEY_SESSION_ID); SessionCache.sessionId = sessionId; stu PID
24. Indescriptive Naming Stup ID
25. Adam Tornhill stup ID public class UserDataSourceImp implements UserDataSource { private User getUser(String id) { User value = map.get(id); if(value != null && value.getType() == 2) { return value; } else { return null; } }
26. Duplication StupI D
27. Adam Tornhill stupI D observable .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe(new Subscriber() { @Override public void onCompleted() {} @Override public void onError(Throwable e) {} @Override public void onNext(String value) {}); }
28. SOLID
29. Single Responsibility SOLID
30. Adam Tornhill SOLID public class MainActivity extends Activity { public void onCreate() { userApi.getUser(getExtraUserId()) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe(this::RenderUser); } }
31. Adam Tornhill SOLID public class MainActivity extends Activity { public void onCreate() { controller.getUser(this::RenderUser); } }
32. Open / Close S OLID
33. Adam Tornhill S OLID public class FeedAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { public void onBindViewHolder (ViewHolder holder, int position) { FeedEntry feedEntry = entries.get(position); if (feedEntry instanceOf AdsEntry) { renderAds(feedEntry); } else { renderEntry(feedEntry); } }
34. Adam Tornhill S OLID public class FeedAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { public void onBindViewHolder (ViewHolder holder, int position) { FeedEntry feedEntry = entries.get(position); FeedRow row = feedFactory.get(feedEntry); row.render(); }
35. Liskov Substitution So LID
36. Adam Tornhill SO LID context.startActivity(startActivity);
37. Adam Tornhill SO LID ¯\_(ϑ)_/¯
38. Interface Segregation SOL ID
39. Adam Tornhill SOL ID public static interface AnimatorListener {
 void onAnimationStart (Animator animation);
 void onAnimationEnd (Animator animation);
 void onAnimationCancel (Animator animation); void onAnimationRepeat (Animator animation);
 }
40. Adam Tornhill SOL ID public class EmptyAnimatorListener implements AnimatorListener {
 void onAnimationStart (Animator animation) {}
 void onAnimationEnd (Animator animation) {}
 void onAnimationCancel (Animator animation) {} void onAnimationRepeat (Animator animation) {}
 }
41. Dependency Inversion SOLI D
42. Adam Tornhill SOLI D new CursorLoader(…)
43. Adam Tornhill SOLI D Loader loader = LoaderBuilder .withURI(uri) .create();
44. Open your mind Take ideas from other languages and technologies
45. Find me I am very social! jorge@karumi.com @flipper83 +JorgeJBarroso Questions?