Android Software Architecutre by Example

Comparing some architectural design patterns like MVC, MVP, MVVM, Redux, Flux, MVI and how they could be applied on existing open source applications.

Youtube video: https://www.youtube.com/watch?v=7t7MN8e1W7s

Transcript

3. HELLO I’m Hannes
4. ANDROID ARCHITECTURE BY EXAMPLE
5. SLOWED DOWN BY BAD CODE?
6. FEAR CHANGING CODE!
7. SOLID Robert C. Martins
 „Uncle Bob“
8. SINGLE RESPONSIBILITY “A class should only have one reason to change” Book 
 currentPage() nextPage() print()
9. SINGLE RESPONSIBILITY “A class should only have one reason to change” Book 
 currentPage() nextPage() print() Book 
 currentPage() nextPage() Printer 
 print(Book)
10. FUNCTIONAL PROGRAMMING
11. FOCUS ON WHAT NOT ON HOW
12. public Map<String, Integer> xxx(String[] words){
 Map<String, Integer> countMap = new HashMap();
 
 for (String word : words ) {
 Integer count = countMap.get(word);
 if (count == null)
 countMap.put(word, 1);
 else
 countMap.put(word, count + 1);
 }
 return countMap;
 }
13. public Map<String, Integer> countWords(String[] words){
 Map<String, Integer> countMap = new HashMap();
 
 for (String word : words ) {
 Integer count = countMap.get(word);
 if (count == null)
 countMap.put(word, 1);
 else
 countMap.put(word, count + 1);
 }
 return countMap;
 }
14. fun countWords(words: Array<String>) : Map<String, Int> { val grouped: Map<String, List<String>> = words.groupBy { word -> word }
 val countMap: Map<String, Int> = grouped.mapValues { entry -> entry.value.size }
 return countMap }

15. fun countWords(words: Array<String>) : Map<String, Int> { return words.groupBy { word -> word } .mapValues { entry -> entry.value.size } }

16. public Pair<String, Integer> mostFrequent( String[] words, int threshold) {
 Pair<String, Integer> mostFrequent = null;
 Map<String, Integer> countMap = countWords( words );
 
 for (Map.Entry<String, Integer> entry : countMap.entrySet() ) {
 if (entry.getValue() < threshold)
 continue;
 if (mostFrequent == null || entry.getValue() > mostFrequent.second)
 mostFrequent = new Pair(entry.getKey(), entry.getValue());
 }
 
 return mostFrequent;
 }
17. fun mostFrequent(words: Array<String>, threshold: Int) : Pair<String, Int> { return countWords(words) // Map<String, Int>
 .toList() // List<Pair<String, Int>>
 .sortedBy { pair -> pair.second }
 .filter { pair -> pair.second > threshold }
 .first()
 }
18. IMMUTABILITY
20. You want an 
 immutable hot dog
21. AUTOVALUE @AutoValue public abstract class HotDog { }
22. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable { }
23. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); }
24. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); @ColumnName public abstract boolean hasKetchup(); }
25. AUTOVALUE @AutoValue public abstract class HotDog implements Parcelable {
 @Json public abstract double getPrice(); @ColumnName public abstract boolean hasKetchup(); public abstract static HotDog(double p, boolean k) { return new AutoValue_HotDog(p, k); } }
26. MVC Model-View-Controller
27. MVC Trygve Reenskaug View Model Controller observes changes
29. ARCHITECTURE BY EXAMPLE
30. OMNI-NOTES • https://github.com/federicoiosue/Omni-Notes • 506 Stars on Github • Last commit: 31st of May 2016 • 4,4 Rating • 100.000 - 500.000 installs 2nd June 2016
32. OMNI-NOTES • Fragments + Activities • AsyncTask with WeakReference as Callback • AsyncTask with EventBus • Database + File Storage 2nd June 2016
33. REDUX Predictable State Container
34. REDUX • Store • Action • Reducer
35. REDUX • Store - state container of the Model (immutable) • Action • Reducer
36. REDUX • Store - state container of the Model (immutable) • Action - command to change Model’s state • Reducer
37. REDUX • Store - state container of the Model (immutable) • Action - command to change Model’s state • Reducer - function (action , oldState) 㱺 newState
38. PURE FUNCTION public class Calculator {
 
 int result = 0;
 
 public int add(int x){
 result = x + result;
 return result;
 }
 }
39. –Robert C. Martins „The root of all evil is the assignment statement“
40. PURE FUNCTION public class PureCalculator {
 
 public int add(int x, int y){
 return x + y;
 }
 }
41. REDUX • Store - state container of the Model (immutable) • Action - command to change Model’s state • Reducer - function (action , oldState) 㱺 newState
42. OmniModel notes […],
43. OmniModel notes […], AddNoteAction title, description …
44. OmniModel notes […] AddNoteAction title, description … public OmniModel reduce(Action a, OmniModel old){
 if (a instance AddNoteAction){ OmniModel newModel = oldModel.withNotes(old.notes + a.newNode) return newModel; }
 …
45. AddNoteAction title, description … Store reduce(a, m) OmniModel notes […]
46. Store AddNoteAction title, description … reduce(a, m) OmniModel notes […] store.subscribe(this)
47. Store reduce(a, m) OmniModel notes […] store.subscribe(this) store.dispatch( )
48. Store reduce(a, m) OmniModel notes […] store.subscribe(this)
49. Store reduce(a, m) OmniModel notes […] store.subscribe(this) notify(model)
50. Store reduce(a, m) OmniModel notes […], orderBy: … notify(model) OrderByAction order: last modification store.dispatch()
51. Store reduce(a, m) OmniModel notes […], orderBy: … notify(model) OrderByAction order: last modification store.dispatch() notify(model)
52. REDUX • Immutability • Unidirectional data flow • pure function
53. TELEGRAM • https://github.com/DrKLO/Telegram • 4999 Stars on Github • Last commit: 26th of May 2016 • 4,2 Rating • 100.000.000 - 500.000.000 installs 2nd June 2016
55. TELEGRAM • MessageController, ContactsController … • Singletons, no dependency injection • Many classes are using these „Controllers“ • Classes with 1000+ lines of code
56. FLUX
58. ShowListAction
60. MessageStore ContactsStore
61. PushNotification
 MessageReceivedAction
62. FLUX • only public getters in Store API • Unidirectional data flow
63. FLUX VS. MVC* • Store ≈ Model • View ≈ Controller • unidirectional dataflow! *Not Reenskaug MVP
64. TWIDERE • https://github.com/TwidereProject/Twidere-Android • 873 Stars on Github • Last commit: 16th of May 2016 • 4,1 Rating • 100.000 - 500.000 installs 2nd June 2016
66. TWIDERE • AbstractTask ≈ AsyncTask + WeakReference + EventBus • ContentResolver + ContentObserver • Tasks are doing a lot • Fragments & Activities are small ( < 500 Lines of Code) • Dependency Injection (Dagger 2)
69. MVVM Model-View-ViewModel
71. public class TweetModel {
 
 public ObservableString message;
 
 public ObservableInt stars;
 } Not immutable! Code in XML?
 Error State? Loading Indicator?
72. REACTIVE PROGRAMMING
73. java.util.Observable
74. https://www.youtube.com/watch?v=uNZnftSksYg
75. RxBus
76. MVVMC Model-View-ViewModel-Controller
77. FeedController HomeFeedViewModel loadCommand() : Observable HomeFeedActivity TwitterApi
78. FeedController HomeFeedViewModel loadCommand() : Observable HomeFeedActivity TwitterApi subscribe to loadCommand() ContentProvider
79. PLAID • https://github.com/nickbutcher/plaid • 5170 Stars on Github • Last commit: 1st of June 2016 • 5.000 - 10.000 installs 2nd June 2016
81. PLAID • No clear Separation of responsibilities • AsyncTask • Android Services • Shared Preferences for persistency 2nd June 2016
82. CLEAN ARCHITECTURE Robert C. Martins
83. CLEAN ARCHITECTURE Entity Entity Entity Interactor
 Presenter
 View

84. CLEAN ARCHITECTURE Entity Entity Entity Interactor
 Presenter
 View
 Break the Rules! https://publicobject.com/2016/04/20/deliberate-disobedience/
86. MVI Model-View-Intent
87. cycle.js.org
88. intent( )
89. model( intent( ) )
90. view( model( intent( ) ) )
91. view( model( intent( ) ) ) new Model displayed by View Intent changes Model UI Events start intents
92. interface SearchView {
 Observable<String> searchIntent();
 void showResult(SearchResult res);
 }
93. interface SearchView {
 Observable<String> searchIntent();
 void showResult(SearchResult res);
 } class SearchResult {
 List<Item> result; boolean loading; boolean error;
 }
94. interface SearchView {
 Observable<String> searchIntent();
 void showResult(SearchResult res);
 } class SearchResult {
 List<Item> result; boolean loading; boolean error;
 } class SearchEngine {
 Observable<SearchResult> search(Observable<String> s){ … } }
95. interface SearchView {
 Observable<String> searchIntent();
 void showResult(SearchResult res);
 } class SearchResult {
 List<Item> result; boolean loading; boolean error;
 } class SearchEngine {
 Observable<SearchResult> search(Observable<String> s){ … } } class SearchPresenter {
 void attachView(SearchView v){ searchEngine.search(v.searchIntent()) .subscribe(v::showResult) } }
100. -Someone Smart „If you like the code you have written a year ago you haven’t learned enough this year“
101. REFERENCES • https://github.com/reactjs/redux • http://facebook.github.io/flux/ • https://www.youtube.com/watch?v=uNZnftSksYg&t=757s • https://github.com/bkase/cyklic • http://cycle.js.org/
102. THANK YOU QUESTIONS? hannesdorfmann.com @sockeqwe