From Legacy to Hexagonal Android (Droidcon London 2014)

Transcript

1. From Legacy to Hexagonal (Android) Rubén Serrano @Akelael Lead Android Developer @RedboothHQ
2. Agenda 1. From Legacy Code 2. Towards Hexagonal Architecture 3. To infinity, and beyond!
3. 1. From Legacy Code
4. Meet the team
7. ! ! 1. One dev from a contractor
8. ! ! 2. One dev from a contractor + one senior iOS dev
9. ! ! 3. One dev from a contractor + one senior iOS dev
10. ! ! 3. One dev from a contractor + one senior iOS dev one junior iOS dev
11. ! ! 4. One dev from a contractor + one senior iOS dev one junior iOS dev
12. ! 4. A different Android dev + One dev from a contractor one senior iOS dev one junior iOS dev
13. ! 5. A different Android dev + One dev from a contractor one senior iOS dev one junior iOS dev + one confused Android team
14. Meet the code
16. Meet the problem
17. 1. We have a huge technical debt
18. 1. We have a huge technical debt
19. HUGE
20. 1. We have huge technical debt 2. We can’t stop developing new features
21. 1. We have huge technical debt 2. We can’t stop developing new features 3. We can’t remove debt at this point
22. 1. We have huge technical debt 2. We can’t stop developing new features 3. We can’t remove debt at this point 4. We shouldn’t increase our technical debt
23. 2. Towards Hexagonal
24. Working with legacy code
25. Read this book
26. Model View Presenter
27. In theory
28. View Presenter Model
29. View Presenter Model Notifies events
30. View Presenter Model Requests data
31. View Presenter Model Serves data
32. View Presenter Model Change data representation
33. View Presenter Model Tells how to draw
34. Layout + Activity/ Fragment Presenter Data + Business logic
35. In code (Original code…) http://goo.gl/z5Xn2J
36. listAdapter =
 new SimpleCursorAdapter(getActivity(),
 android.R.layout.simple_list_item_1,
 null,
 new String[]{FakeDatabase.COLUMN_NAME},
 new int[]{android.R.id.text1},
 0);
 listView.setAdapter(listAdapter); MainFragment
37. ! 
 getLoaderManager().initLoader(0, null, new LoaderManager.LoaderCallbacks<Cursor>() {
 @Override
 public Loader<Cursor> onCreateLoader(int id, Bundle args) {
 return new CursorLoader(getActivity(), MainContentProvider.URI, null, null, null, null);
 }
 
 @Override
 public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
 listAdapter.swapCursor(data);
 }
 
 @Override
 public void onLoaderReset(Loader<Cursor> loader) {
 listAdapter.swapCursor(null);
 }
 }); MainFragment
38. In code (… to MVP) http://goo.gl/Retvli
39. MainView & MainModel public interface MainView {
 public void swaplListData(Cursor cursor);
 } ! public interface MainModel {
 public void setPresenter(MainPresenter presenter);
 public void startLoadingData(Context context);
 }

40. MainFragment public class MainFragment extends Fragment implements MainView {
 //...
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 presenter = PresenterFactory.getMainPresenter(this);
 } ! @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 presenter.notifyOnCreate(getActivity());
 } ! @Override
 public void swaplListData(Cursor cursor) {
 listAdapter.swapCursor(cursor);
 }
41. MainPresenter public class MainPresenter {
 private MainView mainView;
 private MainModel mainModel;
 
 //...
 
 public void notifyOnCreate(Context context) {
 mainModel.startLoadingData(context);
 }
 
 public void notifiyLoadedDataAvailable(Cursor cursor) {
 mainView.swaplListData(cursor);
 }
 }
42. PresenterFactory public class PresenterFactory {
 public static MainPresenter getMainPresenter(MainView view) {
 MainModel model = new MainCursorModel();
 return MainPresenter.newInstance(view, model);
 }
 }
43. MainCursorModel public class MainCursorModel implements MainModel {
 //... 
 @Override
 public void startLoadingData(Context context) {
 new LoadDataAsyncTask().execute(context);
 }
 
 private class LoadDataAsyncTask extends AsyncTask<Context, Void, Cursor > {
 //... 
 @Override
 protected void onPostExecute(Cursor result) {
 super.onPostExecute(result);
 presenter.notifiyLoadedDataAvailable(result);
 }
 }
 }
44. Pros & Cons View decoupled from model Cleaner code and smaller fragment/activities View and model not really decoupled (cursor) All the components use the framework
45. Hexagonal Architecture
46. In theory
47. Layout + Activity/ Fragment Presenter Data + Business logic
48. Layout + Activity/ Fragment Data domain Logic
49. Layout + Activity/ Fragment Database Logic Network Sensors
50. Sensors Network Database Layout + Activity/ Fragment Logic
51. Logic Sensors Network Database Layout + Activity/ Fragment
52. Logic Sensors Network Database Layout + Activity/ Fragment Port Port Port Port
53. Logic Sensors Network Database Layout + Activity/ Fragment Port Port Port Port Adapter Adapter Adapter Adapter
54. Logic Sensors Network Database Layout + Activity/ Fragment Port Port Port Port Adapter Adapter Adapter Adapter
55. Logic Sensors Network Database Layout + Activity/ Fragment Port Port Port Port Boundary Boundary Boundary Boundary
56. Module Core Module App Module App Module App Module App Core Core Core Core App App App App
57. In code (Hexagonal) http://goo.gl/lIyH0o
58. MainFragment public class MainFragment extends Fragment {
 //...
 private MainFragmentBoundary viewBoundary;
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
 //...
 viewBoundary = MainFragmentBoundary.newInstance(this);
 }
 
 @Override
 public void onActivityCreated(Bundle savedInstanceState) {
 //...
 viewBoundary.notifyOnCreate();
 }
59. MainFragment public void setListAdapter() {
 listAdapter = new ArrayAdapter<String>(getActivity(),
 android.R.layout.simple_list_item_1,
 android.R.id.text1,
 new ArrayList<String>(0));
 listView.setAdapter(listAdapter);
 }
 
 public void swapList(List<String> names) {
 listAdapter.clear();
 listAdapter.addAll(names);
 }
60. MainFragmentBoundary public class MainFragmentBoundary implements MainViewPort {
 private MainFragment mainFragment;
 private MainLogic logic;
 
 //...
 public void notifyOnCreate() {
 logic.notifyOnCreate();
 } 
 @Override
 public void swaplListData(List<String> names) {
 mainFragment.swapList(names);
 }
61. MainModelBoundary public class MainModelBoundary implements MainModelPort {
 private MainLogic logic;
 private MainRepository repository;
 //...
 
 @Override
 public void startLoadingData() {
 repository.startLoadingData(new MainRepository.OnDataLoadedListener() {
 @Override
 public void onDataLodaded(Cursor cursor) {
 notifyDataLoaded(cursor);
 }
 });
 }
 
 private void notifyDataLoaded(Cursor cursor) {
 List<String> names = mapCursorToList(cursor);
 logic.notifiyLoadedDataAvailable(names);
 }
62. MainModelBoundary private List<String> mapCursorToList(Cursor cursor) {
 List<String> names = new ArrayList<String>();
 int nameColumnIndex = cursor.getColumnIndex(FakeDatabase.COLUMN_NAME);
 while (cursor.moveToNext()) {
 String name = cursor.getString(nameColumnIndex);
 names.add(name);
 }
 return names;
 }
63. Pros & Cons Logic is not going to be affected by framework changes Logic is pure Java: easier to test Less changes when replacing a plugin Easier for 2 devs to work on the same feature More complex architecture Need to map each POJO for each layer What happens when the plugins need to cooperate?
64. 3. To infinity, and beyond!
65. One plugin, N commands
66. Logic Sensors Network Database Layout + Activity/ Fragment Port Port Port Port Boundary Boundary Boundary Boundary
67. Logic Model plugin Layout + Activity/ Fragment Port Port Boundary Boundary
68. Create task Send chat message Logic Model plugin Port Boundary Update note Request projects
69. Asynchrony
70. Create task Send chat message Update note Request projects Logic Model plugin Port Boundary
71. Create task Send chat message Update note Request projects Logic Model plugin Port Boundary
72. We don’t like: callback’s hell + AsyncTasks
73. We don’t like: callback’s hell + AsyncTasks We don’t mind (but could be a problem): only commands in separate threads
74. We don’t like: callback’s hell + AsyncTasks We don’t mind (but could be a problem): only commands in separate threads We would love: RxJava
75. Use cases
76. Logic Model plugin Layout + Activity/ Fragment Port Port Boundary Boundary
77. Use case Model plugin Layout + Activity/ Fragment Presenter Use case Use case Model plugin Model plugin
78. Conclusions photo by Daniel Sancho
79. When? • If you expect 2+ devs working on the same feature • Unless you are sure the app is going to die in a near future • You know for sure you will change your plugins
80. How? 1. Simple refactors 2. Model View Presenter 3. Hexagonal 4. Add some technical debt?
81. Thank you!
82. Questions? Rubén Serrano @Akelael