Talk about what MVP means to different people and how using MVP doesn't even matter. It's about the discussion. I've hacked an app together with MVP, I want to show my findings and opinions about the most over defined term for a pattern ever.

1. Most Volatile Palaver
Paul Blundell
MVP examined holistically and subjectively

2. My Vision Program
- Highlight the variations
- Talk about the conflictions
- Define the naming
- Example implementation
- Emphasize important points
- Get Pragmatic

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Oh you know MVP?

4. Oh you know MVP?
http://www.wildcrest.com/Potel/Portfolio/mvp.pdf
http://martinfowler.com/eaaDev/uiArchs.html
https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93presenter
https://msdn.microsoft.com/en-us/library/ff649571.aspx
https://github.com/konmik/konmik.github.io/wiki/Introduction-to-Model-View-Presenter-on-
Android
http://c2.com/cgi/wiki?ModelViewPresenter http://www.gwtproject.org/articles/mvp-
architecture.html https://www.youtube.com/watch?v=oiNfPjV72lg
http://polymorphicpodcast.com/shows/mv-patterns/
https://developer.ibm.com/open/2015/10/22/model-view-presenter-mvp-for-ibm-ready-
apps/ https://caster.io/episodes/episode-48-model-view-presenter-part-1-what-is-the-
mvp-pattern/ http://fernandocejas.com/tag/model-view-presenter/
http://engineering.remind.com/android-code-that-scales/
http://antonioleiva.com/mvp-android/
http://geekswithblogs.net/nharrison/archive/2008/09/22/125373.aspx

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P
V

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https://leanpub.com/software-architecture-for-developers https://leanpub.com/visualising-software-architecture

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I know MVP
No I know MVP
No. I know MVP

10. Ivory Tower Syndrome
- My MVP works so it should work
everywhere
- My MVP is the only possible architecture
- Non collaboration
- Lack of discussion of the details
further reading: http://techdistrict.kirkk.com/2009/11/03/turtles-and-architecture/

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Indecent Exposure (42):
This smell indicates the lack of
what David Parnas so famously
termed information hiding. The
smell occurs when methods or
classes that ought
not to be visible to clients are
publicly visible to them. Exposing
such code means that
clients know about code that is
unimportant or only indirectly
important. This contributes
to the complexity of a design.

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16. Here is another opinion!
- Hangover Cures is an app I wrote back in 2012
- Two screens, a list of hangover cures, individual details
- All code was in the Activity
- Added new feature:
Now has a comment
stream, for people to leave
comments about the
cures.

17. Model
- Thin layer and a boundary to the rest of the architecture
of the application (in my case ‘clean architecture’)
- It’s not so much a domain model more of a ‘what can be
done on this view’ api
- Model contains the threading choices

18. View
- Passive View (not observing the model)
- Gets information from ViewModel objects
- The Activity as the View on Android
- Treat Android Views like primitives and we always want
to wrap them in a Domain View
- Encapsulate native Android user interaction
mechanisms and define Domain specific ones

19. Presenter
- Has knowledge of Model & View
- Decides on action after user interaction
- Observes the Model for changes
- Decides how View is notified of Model changes
- Doesn’t care about threading
- Never uses primitive Views or native Listeners

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21. Package Structure
- Not necessary for MVP but a
good bedrock to work from
- Feature based
- Clearly see the app’s
concerns
- Minimal learning curve

22. Core / Mobile split
MVP is a UI level architecture it is not an application
architecture
MVP belongs in the mobile module*
The presenter can have Android imports, that’s ok
For application wide architecture see:
https://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html
https://www.novoda.com/blog/hexawhat-architecture/

23. Single Feature Example - Comments
Only the Activity needs to be public
First place to start [Feature]Mvp.java
Classes shaded out not directly involved
in MVP

24. [Feature]Mvp.java
class CommentsMvp {
public interface Model extends Closeable {
...
}
public interface View {
...
}
public interface Presenter {
...
}
- The inner classes allow for great naming
practices and improved readabilty.
- This stops strange things like
CommentsPresenterImpl implements CommentsPresenter
- It also highlights the UI layers MVP pattern
very obviously to the legacy developer

25. CommentsMvp.java Implementers
class CommentsModel implements CommentsMvp.Model {
...
}
public class CommentsActivityView extends AppCompatActivity implements CommentsMvp.View, CommentsStream.Listener {
...
}
class CommentsAnalyticsView implements CommentsMvp.View {
...
}
class CommentsPresenter implements CommentsMvp.Presenter,
CommentsMvp.Model.AdvertRequestLoadedCallback,
CommentsMvp.Model.UserLoadedCallback,
CommentsMvp.Model.CommentSavedCallback,
CommentsMvp.Model.CommentsLoadedCallback,
CommentsMvp.Model.CommentUpdatedCallback {
...
}

26. CommentsMvp.Model
public interface Model extends Closeable {
void loadUser(UserLoadedCallback callback);
void loadAdvertRequest(AdvertRequestLoadedCallback callback);
void loadCommentsFor(Cure cure, SortOrder sortOrder, CommentsLoadedCallback callback);
void saveComment(Cure.Id id, ViewComment comment, CommentSavedCallback callback);
void saveVoteFor(Cure.Id id, ViewComment comment, Vote down, CommentUpdatedCallback callback);
boolean canVoteOnCommentWith(Cure.Id cureId, Comment.Id commentId);
interface CommentSavedCallback {
void onSaved(ViewComment comment);
}
interface UserLoadedCallback {
void onLoaded(String username); // TODO param can be an object containing also users profile pic
}
interface AdvertRequestLoadedCallback {
void onLoaded(AdRequest advertRequest);
}
interface CommentsLoadedCallback {
void onLoaded(List<ViewComment> comments);
}
interface CommentUpdatedCallback {
void onUpdated(ViewComment comment);
}
}
- callbacks here, can be any
observing method
- save/load is a simple pattern
when you don’t have much
client side state
- knowledge of MVP domain
objects
- no knowledge of Android

27. CommentsMvp.Model Implementor
class CommentsModel implements CommentsMvp.Model {
...
private final UseCaseModelAdapter modelAdapter;
private final Log log;
public CommentsModel(UseCaseModelAdapter modelAdapter, Log log) {
this.modelAdapter = modelAdapter;
this.log = log;
}
@Override
public void loadAdvertRequest(final AdvertRequestLoadedCallback callback) {
Subscription subscription = Observable.create(modelAdapter.getAdvertRequest())
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
...
}
- Thin layer that then moves
from MVP architecture to our
back end of the app
architecture
- Injects the logger to allow
dependency inversion
- Controls asynchronicity as
the model knows when its
innards need threads

28. CommentsMvp.Model Implementor
class CommentsModel implements CommentsMvp.Model {
...
private final UseCaseModelAdapter modelAdapter;
private final Log log;
public CommentsModel(UseCaseModelAdapter modelAdapter, Log log) {
this.modelAdapter = modelAdapter;
this.log = log;
}
@Override
public void loadAdvertRequest(final AdvertRequestLoadedCallback callback) {
Subscription subscription = Observable.create(modelAdapter.getAdvertRequest())
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
...
}
- Thin layer that then moves
from MVP architecture to our
back end of the app
architecture
- Injects the logger to allow
dependency inversion
- Controls asynchronicity as
the model knows when its
innards need threads

29. CommentsMvp.Model Implementor
class CommentsModel implements CommentsMvp.Model {
...
private final UseCaseModelAdapter modelAdapter;
private final Log log;
public CommentsModel(UseCaseModelAdapter modelAdapter, Log log) {
this.modelAdapter = modelAdapter;
this.log = log;
}
@Override
public void loadAdvertRequest(final AdvertRequestLoadedCallback callback) {
Subscription subscription = Observable.create(modelAdapter.getAdvertRequest())
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
...
}
- Thin layer that then moves
from MVP architecture to our
back end of the app
architecture
- Injects the logger to allow
dependency inversion
- Controls asynchronicity as
the model knows when its
innards need threads

30. CommentsMvp.View
public interface View {
void create();
void show(ViewCure cure);
void show(String username);
void show(AdRequest advertRequest);
void show(List<ViewComment> comments);
void showInteractionsFor(ViewComment comment);
void update(ViewComment comment);
void notifyAlreadyVoted();
}
- All commanding methods, telling what to
do
- Use ViewModels to pass the data, here
the naming I think lets it down a bit as
ViewCure could be read incorrectly as
“view the cure” rather than “the view cure
model”

31. CommentsMvp.Presenter
public interface Presenter {
void onCreate(ViewCure cure);
void onCommented(String comment);
void onSelected(ViewComment comment);
void onSelectedVoteUp(ViewComment comment);
void onSelectedVoteDown(ViewComment comment);
void onSelectedFilterCommentsByMostPopularFirst();
void onSelectedFilterCommentByNewestFirst();
}
- includes the lifecycle methods
needed
- includes methods that react to user
interaction (i.e. methods you call
inside a click listener)
Want to investigate this for the lifecycle callbacks https://github.com/soundcloud/lightcycle

32. CommentsMvp.Presenter Implementor
class CommentsPresenter implements
CommentsMvp.Presenter,
CommentsMvp.Model.AdvertRequestLoadedCallback,
CommentsMvp.Model.UserLoadedCallback,
CommentsMvp.Model.CommentSavedCallback,
CommentsMvp.Model.CommentsLoadedCallback,
CommentsMvp.Model.CommentUpdatedCallback {
private final CommentsMvp.Model model;
private final CommentsMvp.View view;
private String username;
private ViewCure cure;
…
@Override
public void onCreate(ViewCure cure) {
this.cure = cure;
view.create();
view.show(cure);
model.loadAdvertRequest(this);
model.loadUser(this);
model.loadCommentsFor(cure, SortOrder.MOST_POPULAR_FIRST, this);
}
- observes the model
- knows about the Model and the View
- keeps state
- onCreate it tells the view to create,
populates the view and requests first
load from the model

33. CommentsMvp.Presenter Implementor
class CommentsPresenter implements
CommentsMvp.Presenter,
CommentsMvp.Model.AdvertRequestLoadedCallback,
CommentsMvp.Model.UserLoadedCallback,
CommentsMvp.Model.CommentSavedCallback,
CommentsMvp.Model.CommentsLoadedCallback,
CommentsMvp.Model.CommentUpdatedCallback {
private final CommentsMvp.Model model;
private final CommentsMvp.View view;
private String username;
private ViewCure cure;
…
@Override
public void onCreate(ViewCure cure) {
this.cure = cure;
view.create();
view.show(cure);
model.loadAdvertRequest(this);
model.loadUser(this);
model.loadCommentsFor(cure, SortOrder.MOST_POPULAR_FIRST, this);
}
- observes the model
- knows about the Model and the View
- keeps state
- tells the view to create, populates the
view and requests first load from the
model

34. CommentsMvp.Presenter Implementor
class CommentsPresenter implements
CommentsMvp.Presenter,
CommentsMvp.Model.AdvertRequestLoadedCallback,
CommentsMvp.Model.UserLoadedCallback,
CommentsMvp.Model.CommentSavedCallback,
CommentsMvp.Model.CommentsLoadedCallback,
CommentsMvp.Model.CommentUpdatedCallback {
private final CommentsMvp.Model model;
private final CommentsMvp.View view;
private String username;
private ViewCure cure;
…
@Override
public void onCreate(ViewCure cure) {
this.cure = cure;
view.create();
view.show(cure);
model.loadAdvertRequest(this);
model.loadUser(this);
model.loadCommentsFor(cure, SortOrder.MOST_POPULAR_FIRST, this);
}
- observes the model
- knows about the Model and the View
- keeps state
- tells the view to create, populates the
view and requests first load from the
model

35. CommentsMvp.Presenter Implementor
class CommentsPresenter implements
CommentsMvp.Presenter,
CommentsMvp.Model.AdvertRequestLoadedCallback,
CommentsMvp.Model.UserLoadedCallback,
CommentsMvp.Model.CommentSavedCallback,
CommentsMvp.Model.CommentsLoadedCallback,
CommentsMvp.Model.CommentUpdatedCallback {
private final CommentsMvp.Model model;
private final CommentsMvp.View view;
private String username;
private ViewCure cure;
…
@Override
public void onCreate(ViewCure cure) {
this.cure = cure;
view.create();
view.show(cure);
model.loadAdvertRequest(this);
model.loadUser(this);
model.loadCommentsFor(cure, SortOrder.MOST_POPULAR_FIRST, this);
}
- observes the model
- knows about the Model and the View
- keeps state
- tells the view to create, populates the
view and requests first load from the
model

36. CommentsMvp.Presenter Implementor
…
@Override
public void onSelectedFilterCommentByNewestFirst() {
model.loadCommentsFor(cure, SortOrder.NEWEST_FIRST, this);
}
...
@Override
public void onSaved(ViewComment comment) {
view.update(comment);
}
...
- observes the View and decides what
action to take on user interaction
- observes the Model and decides how
the view should be updated

37. ViewComment
A comment whos responsibilities lie in the view layer
- vs a comment whos responsibilities lie in the domain
layer
- Meaning it can have view centric methods
- getContentDescription, getFormattedDate
- Immutable, only get never set
- Could implement Parcelable

38. CommentsAnalyticsView
- Analytics tracking can be thought
of as another view on the same
presenter
- Uses decorator pattern, could
also be an observer pattern if you
wanted more than two
- Experimental ...
class CommentsAnalyticsView implements CommentsMvp.View {
...
public CommentsAnalyticsView(Tracker tracker, CommentsMvp.View view) {
this.tracker = tracker;
this.view = view;
}
@Override
public void create() {
tracker.setScreenName("Comments");
tracker.send(new HitBuilders.ScreenViewBuilder().build());
view.create();
}
@Override
public void show(Cure cure) {
view.show(cure);
}
…
@Override
public void showInteractionsFor(ViewComment comment) {
tracker.setScreenName("Interaction " + comment.getName());
tracker.send(new HitBuilders.ScreenViewBuilder().build());
view.showInteractionsFor(comment);
}
}

39. Presenter Instantiation
onCreate is in the Activity, newInstance is in the Presenter (or in any factory)
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ViewCure cure = (ViewCure) getIntent().getSerializableExtra(EXTRA_CURE);
HangoverCuresApplication dependencyProvider = (HangoverCuresApplication) getApplicationContext();
presenter = CommentsPresenter.newInstance(dependencyProvider, this);
presenter.onCreate(cure);
}
public static CommentsMvp.Presenter newInstance(HangoverCuresApplication dependencyProvider, CommentsMvp.View view) {
Log log = new AndroidLog();
FirebaseCommentRepository firebase = new FirebaseCommentRepository();
SharedPrefsVoteRepository sharedPrefsVoteRepository = SharedPrefsVoteRepository.newInstance(dependencyProvider.getApplicationContext());
CommentUseCase commentUseCase = new CommentUseCase(firebase);
VotingUseCase votingUseCase = new VotingUseCase(sharedPrefsVoteRepository);
UseCaseModelAdapter useCaseModelAdapter = new UseCaseModelAdapter(commentUseCase, votingUseCase);
CommentsMvp.Model model = new CommentsModel(useCaseModelAdapter, log);
Tracker tracker = dependencyProvider.getAnalyticsTracker();
return new CommentsPresenter(model, new CommentsAnalyticsView(tracker, view));
}

40. Deliberate View language
- Try to consider the domain of your UI (talk to the designers & business
analysts)
- Never end a custom view with the word view
- Avoids communication issues & complications
class CommentsStream extends LinearLayout {
- When using primitive views consider naming them widgets
public class DetailsActivityView extends AppCompatActivity implements DetailsMvp.View {
private DetailsMvp.Presenter presenter;
private TextView titleWidget;
private TextView descriptionWidget;
private RatingBar ratingBarWidget;
private AdView advertWidget;

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SRS TEAM
TIME

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https://github.com/novoda/spikes/tree/master/Architecture

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48. Thanks
blundell_apps
G what?
blundell

49. throw new SlideIndexOutOfBoundsException();
blundell_apps
G what?
blundell
Questions?