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HELLO
I’m
Hannes
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ANDROID ARCHITECTURE
BY EXAMPLE
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SLOWED DOWN
BY BAD CODE?
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FEAR CHANGING CODE!
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SOLID
Robert C. Martins
„Uncle Bob“
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SINGLE RESPONSIBILITY
“A class should only have one reason to change”
Book
currentPage()
nextPage()
print()
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SINGLE RESPONSIBILITY
“A class should only have one reason to change”
Book
currentPage()
nextPage()
print()
Book
currentPage()
nextPage()
Printer
print(Book)
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FUNCTIONAL
PROGRAMMING
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FOCUS ON WHAT
NOT ON HOW
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public Map xxx(String[] words){
Map 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;
}
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public Map countWords(String[] words){
Map 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;
}
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fun countWords(words: Array)
: Map {
val grouped: Map> =
words.groupBy { word -> word }
val countMap: Map =
grouped.mapValues { entry -> entry.value.size }
return countMap
}
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fun countWords(words: Array)
: Map {
return
words.groupBy { word -> word }
.mapValues { entry -> entry.value.size }
}
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public Pair mostFrequent( String[] words, int threshold)
{
Pair mostFrequent = null;
Map countMap = countWords( words );
for (Map.Entry entry : countMap.entrySet() ) {
if (entry.getValue() < threshold)
continue;
if (mostFrequent == null || entry.getValue() > mostFrequent.second)
mostFrequent = new Pair(entry.getKey(), entry.getValue());
}
return mostFrequent;
}
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fun mostFrequent(words: Array, threshold: Int)
: Pair {
return countWords(words) // Map
.toList() // List>
.sortedBy { pair -> pair.second }
.filter { pair -> pair.second > threshold }
.first()
}
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IMMUTABILITY
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You want an
immutable hot dog
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AUTOVALUE
@AutoValue
public abstract class HotDog {
}
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AUTOVALUE
@AutoValue
public abstract class HotDog implements Parcelable {
}
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AUTOVALUE
@AutoValue
public abstract class HotDog implements Parcelable {
@Json
public abstract double getPrice();
}
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AUTOVALUE
@AutoValue
public abstract class HotDog implements Parcelable {
@Json
public abstract double getPrice();
@ColumnName
public abstract boolean hasKetchup();
}
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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); }
}
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MVC
Model-View-Controller
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MVC
Trygve Reenskaug
View
Model Controller
observes
changes
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ARCHITECTURE
BY EXAMPLE
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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
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OMNI-NOTES
• Fragments + Activities
• AsyncTask with WeakReference as Callback
• AsyncTask with EventBus
• Database + File Storage
2nd June 2016
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REDUX
Predictable State Container
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REDUX
• Store
• Action
• Reducer
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REDUX
• Store - state container of the Model (immutable)
• Action
• Reducer
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REDUX
• Store - state container of the Model (immutable)
• Action - command to change Model’s state
• Reducer
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REDUX
• Store - state container of the Model (immutable)
• Action - command to change Model’s state
• Reducer - function (action , oldState) 㱺 newState
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PURE FUNCTION
public class Calculator {
int result = 0;
public int add(int x){
result = x + result;
return result;
}
}
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–Robert C. Martins
„The root of all evil is the assignment statement“
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PURE FUNCTION
public class PureCalculator {
public int add(int x, int y){
return x + y;
}
}
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REDUX
• Store - state container of the Model (immutable)
• Action - command to change Model’s state
• Reducer - function (action , oldState) 㱺 newState
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OmniModel
notes […],
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OmniModel
notes […],
AddNoteAction
title, description …
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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;
}
…
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AddNoteAction
title, description …
Store
reduce(a, m)
OmniModel
notes […]
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Store
AddNoteAction
title, description …
reduce(a, m)
OmniModel
notes […]
store.subscribe(this)
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Store
reduce(a, m)
OmniModel
notes […]
store.subscribe(this)
store.dispatch( )
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Store
reduce(a, m)
OmniModel
notes […]
store.subscribe(this)
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Store
reduce(a, m)
OmniModel
notes […]
store.subscribe(this)
notify(model)
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Store
reduce(a, m)
OmniModel
notes […],
orderBy: …
notify(model)
OrderByAction
order: last modification
store.dispatch()
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Store
reduce(a, m)
OmniModel
notes […],
orderBy: …
notify(model)
OrderByAction
order: last modification
store.dispatch()
notify(model)
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REDUX
• Immutability
• Unidirectional data flow
• pure function
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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
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TELEGRAM
• MessageController, ContactsController …
• Singletons, no dependency injection
• Many classes are using these „Controllers“
• Classes with 1000+ lines of code
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FLUX
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ShowListAction
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MessageStore
ContactsStore
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PushNotification
MessageReceivedAction
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FLUX
• only public getters in Store API
• Unidirectional data flow
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FLUX VS. MVC*
• Store ≈ Model
• View ≈ Controller
• unidirectional dataflow!
*Not Reenskaug MVP
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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
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TWIDERE
• AbstractTask ≈ AsyncTask + WeakReference + EventBus
• ContentResolver + ContentObserver
• Tasks are doing a lot
• Fragments & Activities are small ( < 500 Lines of Code)
• Dependency Injection (Dagger 2)
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MVVM
Model-View-ViewModel
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public class TweetModel {
public ObservableString message;
public ObservableInt stars;
}
Not immutable!
Code in XML?
Error State?
Loading Indicator?
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REACTIVE PROGRAMMING
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java.util.Observable
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https://www.youtube.com/watch?v=uNZnftSksYg
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RxBus
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MVVMC
Model-View-ViewModel-Controller
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FeedController
HomeFeedViewModel
loadCommand() : Observable
HomeFeedActivity
TwitterApi
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FeedController
HomeFeedViewModel
loadCommand() : Observable
HomeFeedActivity
TwitterApi
subscribe to loadCommand()
ContentProvider
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PLAID
• https://github.com/nickbutcher/plaid
• 5170 Stars on Github
• Last commit: 1st of June 2016
• 5.000 - 10.000 installs
2nd June 2016
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PLAID
• No clear Separation of responsibilities
• AsyncTask
• Android Services
• Shared Preferences for persistency
2nd June 2016
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CLEAN ARCHITECTURE
Robert C. Martins
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CLEAN ARCHITECTURE
Entity
Entity
Entity
Interactor
Presenter
View
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CLEAN ARCHITECTURE
Entity
Entity
Entity
Interactor
Presenter
View
Break the Rules!
https://publicobject.com/2016/04/20/deliberate-disobedience/
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MVI
Model-View-Intent
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cycle.js.org
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intent( )
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model( intent( ) )
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view( model( intent( ) ) )
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view( model( intent( ) ) )
new Model
displayed by View
Intent changes Model
UI Events start intents
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interface SearchView {
Observable searchIntent();
void showResult(SearchResult res);
}
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interface SearchView {
Observable searchIntent();
void showResult(SearchResult res);
}
class SearchResult {
List result;
boolean loading;
boolean error;
}
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interface SearchView {
Observable searchIntent();
void showResult(SearchResult res);
}
class SearchResult {
List result;
boolean loading;
boolean error;
}
class SearchEngine {
Observable search(Observable s){
…
}
}
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interface SearchView {
Observable searchIntent();
void showResult(SearchResult res);
}
class SearchResult {
List result;
boolean loading;
boolean error;
}
class SearchEngine {
Observable search(Observable s){
…
}
}
class SearchPresenter {
void attachView(SearchView v){
searchEngine.search(v.searchIntent())
.subscribe(v::showResult)
}
}
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-Someone Smart
„If you like the code you have written a year ago
you haven’t learned enough this year“
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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/
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THANK YOU
QUESTIONS?
hannesdorfmann.com
@sockeqwe