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EXPERIMENTING WITH
ARCHITECTURE FOR
ANDROID
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Tan JunRong
Android Engineer
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Let’s Talk
About Architecture ”
“
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Why?
Do We Really Need It?
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Let’s Consider…
Login Activity
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NO ARCHITECTURE
- Too coupled, hard to swap view/data source/
main logic
- Activity becomes really long, hard to read
- Hard to test, only with Espresso
- etc
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NO ARCH = MVC
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CHOOSING
ARCHITECTURE
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WHICH!?
MVVM
DATABINDING
MVP
UNCLE BOB’S CLEAN ARCH
MVVM
RXJAVA
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https://github.com/googlesamples/
android-architecture
Official Google example on Github
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MVVM
DATABINDING
MVP
MVVM
RXJAVA
Today's Discussion
MVP-VM
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Need an example to compare…
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No Architecture
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No Arch
nameEditText.addTextChangedListener(TextWatcherImp { s, _, _, _ ->
name = s.toString()
updateDisplayString()
})
favoriteAnimalEditText.addTextChangedListener(TextWatcherImp { s,
_, _, _ ->
animalName = s.toString()
updateDisplayString()
})
fun updateDisplayString() {
displayTextView.text = name + " likes " + animalName
}
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Testing Strategy: No Arch
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MVP
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MVP: Activity
nameET.addTextChangedListener({s ->
mvpPresenter.onNameChange(s)
})
favoriteAnimalET.addTextChangedListener({ s ->
mvpPresenter.onAnimalNameChange(s)
})
override fun onDisplayStringUpdate(displayString: String) {
displayTextView.text = displayString
}
Activity {
}
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MVP: Presenter
override fun onNameChange(s: String) {
name = s
displayStringUpdate()
}
override fun onAnimalNameChange(s: String) {
animalName = s
displayStringUpdate()
}
fun displayStringUpdate() {
view.onDisplayStringUpdate(name + " likes " + animalName)
}
Presenter {
}
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Testing Strategy: MVP
1
2
X
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Testing Strategy: MVP practical
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TEST
- Test: states of the screen
- Junit test: lightweight
Code Wise
- Decoupled
- Readability / Consistency
- Swap module (eg. view) easily
MVP: advantage
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MVVM
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MVP
MVVM
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ObservableField
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https://news.realm.io/news/eric-maxwell-mvc-mvp-and-mvvm-on-android/
This MVVM Example
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MVP
MVVM
ViewModel has the same responsibility as Presenter
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https://msdn.microsoft.com/en-us/library/hh848246.aspx
Microsoft MVVM Diagram
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The ViewModel and Presenter looks the same!?
but wait,
ViewModel has something different
consider this…
setting displayString
ViewModel => displayString.set(“JR likes dog”)
Presenter => view.updateDisplayString(“JR likes dog”)
MVP vs MVVM
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ViewModel => displayString.set(“JR likes dog”)
Presenter => view.updateDisplayString(“JR likes dog”)
Key Difference
MVP
MVVM
BOUND!
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OPERATIONS: same responsibility as Presenter in MVP
View Model
STATES: holding the state of views, bound with view
+
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Testing Strategy: MVVM
Not too different from MVP, instead of testing
View.methods(), we test on ViewModel’s state
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RxJava
2 ways of doing MVVM
Data Binding library from Google
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Data Binding library from Google
I use RxJava before trying this lib
I find it hard to use
logic inside XML, cannot be tested
android:visibility =
"@{viewModel.diplayString != null ? View.VISIBLE : View.GONE}"
also,
RxJava provides more, manipulating streams
https://medium.com/@Miqubel/4-reasons-im-not-using-android-data-binding-e62127c2650c
google this term: android data binding library bad idea
”
“
Observable is not compatible with RxJava
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RxJava
Easier to use (if you’re already using RxJava)
no spaghetti code inside xml
you can do more, manipulating streams
viewModel.displayStringObservable.subscribe {
displayTextView.text = it
}
https://github.com/worker8/learning-architecture-for-android
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MVVM: advantage (SAME AS MVP)
Key Difference
- Deal with ViewModel, not View
- (VM is bound to View automatically)
TEST
- Test: states of the screen
- Junit test: lightweight
Code Wise
- Decoupled
- Readability
- Swap module (eg. view) easily
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instead of checking view.action()
My Opinion
I like MVVM more
I can test on view state directly
from ViewModel
disadvantage of mvvm: data binding library,
remedied by RxJava
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Test out yourself before choosing
How to Choose?
Remember the problem you’re trying to solve with arch
Don’t focus on the solution!
For trivial app, use no-architecture
If project uses RxJava, use MVVM
otherwise: use MVP
personal advice…
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MVVM
DATABINDING
MVP
MVVM
RXJAVA
Today's Discussion
MVP-VM
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state +
operations
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state +
operations
what if we place operations
back to Presenter?
ViewModel only hold states now
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MVVM
MVP-VM
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Since VM is separated, I’ll call it MVP-VM
MVP-VM?
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What difference does it make?
persist
MVP-VM
VM
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what does it mean?
persist
MVP-VM
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Observable.combineLatest(input.name, input.favoriteAnimal, {
name, favoriteAnimal ->
MvpVmViewModel(name, favoriteAnimal, name + " likes " +
favoriteAnimal)})
.subscribe(outputViewModel)
I’m making new MvpVmViewModel in every mutation
MvpVmViewModel
MvpVmViewModel
MvpVmViewModel
MvpVmViewModel
MVP-VM
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Save state of screen to DB
Example:
Cookpad recipe
editor page
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Beyond that?
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Since we have all the states of view…
if we store them can we replay it?
yes, but not quite yet…
Hmmm….
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REDUX
Contract: Action
No side effect: Pure reducer
https://egghead.io/courses/getting-started-with-redux
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Android Studio Plugin
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https://github.com/worker8/learning-architecture-for-android/pull/1
Example done using Redux style
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https://github.com/worker8/learning-architecture-for-android
Github example
https://github.com/kittinunf/remote-redux-devtools-android
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Uncle Bob’s clean architecture
What else is Out there?
Redux : Front End Development
VIPER: iOS
https://medium.com/ios-os-x-development/ios-architecture-patterns-ecba4c38de52
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