This document discusses clean architecture principles for Android applications. It outlines goals of having an architecture that is focused on use cases, easy to maintain and test, and decoupled. It describes layers including entities, use cases, interface adapters, frameworks/drivers, presentation layer, and data layer. It emphasizes separating domains, business rules in their own layer, and testing at different levels. Tools mentioned include dependency injections, Proguard, and Lint.

1. Clean architecture: Android
Michał Szczepanik

2. WroDroid

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I have a Dream...

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What a Terrible Failure!

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What is Architecture?

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Architecture is About Intent, not Frameworks
„

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Our goal(s)
● Architecture focused on use cases and main
system function
● Clear use cases first!
● Easy to maintain
● Fast to test
● Easy to test
● Very cohesive
● Decoupled

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Step 0 (setup?)

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Architect role

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Team Role

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Android best practices ?

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Entities
The business objects of the application

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Use Cases
Use Cases orchestrate the flow of data to and
from the entities.
They are also called Interactors.

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Interface Adapters
This set of adapters convert data from the format
most convenient for the use cases and entities.
Presenters and Controllers belong here.

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Frameworks and Drivers
This is where all the details go: UI, tools,
frameworks, etc.

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How to be clean ?

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App architecture – android view

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App architecture – developer view
Presentation
Layer
Domain/Business
Layer
Data
Layer
Entities Layer
Interactors
Boundaries

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Domain (Business) Layer
● Application business rules
● All use cases (interactors)
● Android independent

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Domain (Business) Layer
Domain/Business
Layer
Entities Layer
InteractorsInterfaces
Repository(Dataaccess)Interface
● Interactors Implementation
● Use entities objects
● Most tests are here
● (JUnit plus mockito)

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Entities Layer
● Basic (minimal) business object
● Object's structure
● Low-level rules
● General truths
● Android independent
● Framework independent

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Entities Layer
● Basic java object
● No frameworks
● Test for business objects
● No mocks and stubs
Domain/Business
Layer
Entities Layer
Interactors
Boundaries

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Presentation Layer
● Logic related to UI (view and animation)
● Logic related to Activity and application lifecycle
● Fragments and Activities are only views!
● Design: MVP/MVC/MVVM pattern
● Strongly connected with Android SDK

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Presentation Layer
● Frameworks
● Integration (platform) tests
● UI tests
● (Android Instrumentation)
● (Robotium/Espresso)
● (Robolectric)
Presentation
Layer
Interactors

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Data Layer
● Deliver data needed by app
● Cache
● Service
● Design: with Repository Pattern

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Data Layer
● Repository Pattern
● Integration tests
● Unit tests
● (JUnit plus mockito)
● (Robolectric)
Implementation
RepositoryInterface
Memory
(cache)
Disk
(DB/File)
Cloud

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Testing
● Low-level tests are fast
● High-level tests are slow
● UI testing sucks ?
● Self testing code ?
● new bug = new test

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QA Team

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Monkey
adb shell monkey [options] <event-count>
-s <seed>
-v <verbosity level>

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Android Tips

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65K
Unable to execute dex: method ID not in [0, 0xffff]: 65536
Conversion to Dalvik format failed: Unable to execute dex: method ID
not in [0, 0xffff]: 65536

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How to solve it
● Find reason
– dex-method-counts
● jarjar
● Shrinking libs via Proguard
● Multidex

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Dalvik / ART
● Dalvik:
– Register-based machine
– Just in time (JIT): 2.3+
● ART
– Ahead-of-time (AOT)

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Tools?

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Lint
● Static Code Analysis
● Layouts tips and optimization
● Missing translations
● Layout performance problems
● Unused resources
● Inconsistent array sizes
● Accessibility and internationalization problems
● Icon problems
● Usability problems
● Manifest errors

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Dependency Injections
● Dagger
● RoboGuice

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Injections
● ButterKnife
● AndroidAnnotations

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Injections
class ExampleActivity extends Activity {
@InjectView(R.id.title) TextView title;
@InjectView(R.id.subtitle) TextView subtitle;
@InjectView(R.id.footer) TextView footer;
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_activity);
ButterKnife.inject(this);
// TODO Use "injected" views...
}
}

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Proguard / Dexguard
● Shrinking
● Optimize
● Obfuscate

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Developer options

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Clean Architecture
● Easy to maintain
● Easy to test
● Very cohesive
● Decoupled

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WroDroid
http://www.meetup.com/WroDroid/
Clean Architecture by Unkle Bob
http://goo.gl/Z4zMHG
Architecting Android…The clean way
http://goo.gl/MF13E1
Effective Android UI
http://goo.gl/1dZxfb

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Thank you for your attention

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Questions ?
michal.szczepanik@blstream.com