Clean code on Android (Droidcon Dubai 2015)
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How to write beautiful and clean code on android. From Robert C. Martins book to android specifics, best practises, dependency injection, code smells
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Clean code on Android (Droidcon Dubai 2015)
- 1. Clean Code on Android! DroidCon Dubai Danny Preussler Groupon The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938
- 2. Groupon is the global leader in local commerce, making it easy for people around the world to search ! and discover great businesses at unbeatable prices. Source: Internal data,, March 2014 WORLDWIDE! 260M+ subscribers 53.9M active customers 500+ markets 900M+ deals sold 2 $5B+ in annual billings 12,000+ global employees
- 3. Leading the way in mobile commerce Our mobile app is available in 43 countries. Groupon’s vibrant mobile marketplace connects! consumers with their local economy 3 Sources: Internal Data; iTunes ranking for US stores available here - https://itunes.apple.com/WebObjects/ MZStore.woa/wa/viewFeature?id=500873243&mt=8&v0=www-itunes25Bcountdown-appstore Nearly 110 million people worldwide have downloaded our mobile app at the end of Q4 2014. One of the 25 most downloaded free apps of all time More than 50% of our Global transactions were completed on a mobile device by the end of Q4 2014
- 4. Groupon Berlin Groupon Merchant App Obsessed with beautiful code
- 5. SOLID FOUNDATIONFlughafen Berlin-Brandenburg, Blick in die Abflughalle by Muns CC BY 3.0 http://commons.wikimedia.org/wiki/File:120513-BER-innen.JPG
- 6. violating the most basics principles of Software Engineering! flickr.com/photos/cobblucas/4831501753, Stop by Lucas Cobb, CC by 2.0
- 7. Separation of concerns (1974)! • Modularize, Encapsulate, Layer! Example: Don‘t do HTTP request in Activities/Fragments! flickr.com/photos/ionics/6337522871, Black Sheep Meets White Sheep by Leon Riskin, CC by 2.0
- 8. Don‘t ! repeat ! ourself!! Boris Bikes DLR, Les Haines, CC by 2.0 flickr.com/photos/leshaines123/8370292862
- 9. ViolaTons of DRY are typically referred to as WET soluTons, which is commonly taken to stand for either "write everything twice" or "we enjoy typing” (h<p://en.wikipedia.org/wiki/Don't_repeat_yourself) Android Firewall by Uncalno, CC BY 2.0 flickr.com/photos/uncalno/8538679708
- 10. Clean Code!! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Clean Code by Robert C. Mar0n
- 11. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: (Keep it) small!
- 12. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: Do One Thing!
- 13. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: One Level of Abstrac0on per Func0on!
- 14. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: Reading Code from Top to BoHom
- 15. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: Comments Do Not Make Up for Bad Code
- 16. Robert C. Martin – Clean Code! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 Uncle Bob says: Avoid switch It’s [..] hard to make a switch statement that does one thing. By their nature, switch statements always do N things.
- 17. Much more...! The Living Room, Colin and Sarah Northway, CC by 2.0 h<ps://www.flickr.com/photos/apes_abroad/1479254938 A must Read!
- 18. Codesmells....! Sintra, Portugal, The smell of the portuguese wine, CC by
- 19. Si_ng in a Tree, Big Bend NaTonal Park by Adam Baker, CC by 2.0, flickr.com/photos/atbaker/5474766579 Watch out for ! Primitive Obsession!
- 20. Ban null ! from ! your code!! nothing is nothing by darwin Bell, CC by 2.0, flickr.com/photos/darwinbell/272818496
- 21. private MyParcelable myParceable; ... Bundle bundle = getArguments(); if (bundle != null) { myParceable = bundle.getParcelable("ARGUMENT"); } .... if (myParcaeable != null) { ... } ... if (myParcaeable != null) { ... } Don‘t:! Red Stop Bu<on by Ben K Adams, CC by 2.0, flickr.com/photos/schtumple/5475697999
- 22. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 Do: Inject Dependencies! private MyParcelable myParceable = MyParceable.NONE; ... Bundle bundle = getArguments(); if (bundle != null && bundle.hasParceable(„ARGUMENT“) { myParceable = bundle.getParcelable("ARGUMENT"); } .... if (myParcaeable != null) { ... } ... if (myParcaeable != null) { ... }
- 23. The power of Dependency Injection! • Don‘t create dependencies • Invert Control! • Inject them! I love the Light & I dig the Sun by fady habib, CC by 2.0, flickr.com/photos/unTtlism/2609684221
- 24. public class WetFragment extends Fragment { MyController controller; ... @Override public void onAttach(Activity activity) { super.onAttach(activity); controller = new MyController(activity.getApplicationContext()); Don‘t:! Red Stop Bu<on by Ben K Adams, CC by 2.0, flickr.com/photos/schtumple/5475697999
- 25. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 public class DryFragment extends Fragment { @Inject MyController controller; ... @Override public void onAttach(Activity activity) { super.onAttach(activity); controller = new MyController(activity.getApplicationContext()); Do: Inject Dependencies!
- 26. public class WetFragment extends Fragment { EditText myEditField; @Override public View onCreateView(LayoutInflater inflater, ...) { View view = inflater.inflate(...... myEditField = (EditText)view.findViewById(R.id.edit1); ... Don‘t:! Red Stop Bu<on by Ben K Adams, CC by 2.0, flickr.com/photos/schtumple/5475697999
- 27. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 public class DryFragment extends Fragment { @Inject(R.id.edit1) EditText myEditField; @Override public View onCreateView(LayoutInflater inflater, ...) { View view = inflater.inflate(...... myEditField = (EditText)view.findViewById(R.id.edit1); ... Do: Inject views!
- 28. public class WetFragment extends Fragment { private MyParcelable myParceable; @Override public void onAttach(Activity activity) { super.onAttach(activity); Bundle bundle = getArguments(); if (bundle != null) { myParceable = bundle.getParcelable("ARGUMENT"); if (myParceable == null) { myParceable = MyParcelable.NONE; } } } Don‘t:! Red Stop Bu<on by Ben K Adams, CC by 2.0, flickr.com/photos/schtumple/5475697999
- 29. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 public class DryFragment extends Fragment { @Inject(„ARGUMENT“) MyParcelable = myParceable.NONE; @Override public void onAttach(Activity activity) { super.onAttach(activity); Bundle bundle = getArguments(); if (bundle != null) { myParceable = bundle.getParcelable("ARGUMENT"); if (myParceable == null) { myParceable = MyParcelable.NONE; } } } Do: Inject arguments / extras!
- 30. public class WetFragment extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ...) { return inflater.inflate( R.layout.main_layout, container, false); } Don‘t:! Red Stop Bu<on by Ben K Adams, CC by 2.0, flickr.com/photos/schtumple/5475697999
- 31. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 @InjectLayout(R.layout.main_layout) public class DryFragment extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ...) { return inflater.inflate( R.layout.main_layout, container, false); } Do: Inject layout!
- 32. Cleaner by atomicjeep, CC by 2.0, flickr.com/photos/atomicjeep/144719649 @InjectLayout(R.layout.main_layout) public class DryFragment extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ...) { return inflater.inflate( R.layout.main_layout, container, false); } Do: auto (find) layout! Simply have dry_fragment.xml or dry.xml
- 33. © Biblioarchive, CC by 2.0, www.flickr.com/photos/lac-‐bac/4679195538 • Dagger github.com/square/dagger • Butterknife github.com/JakeWharton/butterknife • InjectExtra github.com/stephanenicolas/injectextra • Autolayout github.com/dpreussler/android-autolayout How to Do:!
- 34. © Biblioarchive, CC by 2.0, www.flickr.com/photos/lac-‐bac/4679195538 • RoboGuice github.com/roboguice/roboguice • Android-Dart github.com/f2prateek/android-dart • Spring Android github.com/spring-projects/spring-android • Transfuse github.com/johncarl81/transfuse • Android Annotations github.com/excilys/androidannotations Alternative or more Do‘s!
- 35. Complicated, Rohit Ma<oo, CC by 2.0, flickr.com/photos/mar00ned/229903286 @Override public void onResume() { super.onResume(); getFragmentManager() .beginTransaction() .add(R.id.fragments, new WetFragment()) . commitAllowingStateLoss(); } Dont: write untestable code:!
- 36. test (c) DaveBleasdale, CC by 2.0, www.flickr.com/photos/sidelong/246816211 Do: write testable code:! @Inject MyTransactionUtil transactions; @Override public void onResume() { super.onResume(); transactions.addAllowingStateLoss( R.id.fragments, new WetFragment()); }
- 37. • Split your Activities • Alternative Mortar github.com/square/mortar Do: use the Power of Fragments! the icon (CC) by MarTn Fisch, CC by 2.0, flickr.com/photos/marfis75/7164769781
- 39. Got legacy code?! Old by Moyan Brenn, flickr.com/photos/aigle_dore/5677012469
- 40. Clean = feel good!! The Living Room, Colin and Sarah Nor h<ps://www.flickr.com/photos/apes_abr
- 41. THANK YOU Danny Preussler GROUPON Berlin dpreussler@groupon.com
- 42. github.com/groupon engineering.groupon.com Michael Burton, Roboguice Carlos Sessa, 50 Android hacks David van der Bokke, RoboRemote David Willson, Odo …. Stephane Nicolas, RoboSpice ParTal Supermen, juliegomoll, CC by 2.0, flickr.com/photos/juliegomoll/1352843346