Denis 2022 Build a scalable, modularized, testable app from scratch From Android Developers 

Architecture 

Architecture(1) Domain Layer (optional) UI Layer Data Layer 

Architecture(2) UI Data Displays data Reacts to changes Business logic Obtains and exposes data Data Events Reactive UI Single source of truth 

Data Layer 

Data Layer(1) Repository Data source Exposes data Centralizes changes Obtains data 

Data Layer(2) Repository NetworkDataSource LocalDataSource Repository REST API DataStore 

Data Layer(3) O ff l ine- fi rst architecture Repository NetworkDataSource LocalDataSource Sync 

UI Layer 

UI Layer(1) Screen State holder Displays UI state Handles UI logic Constructs UI state 

UI Layer(2) UI element ViewModel Repository Repository Jetpack Compose 

UI state composition(1) Repository A Repository B ViewModel UI state Combines/handles data from repositories Loading 

UI state composition(2) Repository A Repository B ViewModel UI state Done Update UI state 

Modularization 

Type of module Responsible for Depends on :app :feature :core Bring features together Single user-facing functionality Single area of common functionality :feature :core :core :core 

https://developer.android.com/topic/modularization 

Testing 

Test dependencies ViewModel Interface Implementation Repository Interface A Repository Interface B Network-DataA-Repository Test-DataA-Repository Local-DataB-Repository Test-DataB-Repository https://developer.android.com/training/testing/fundamentals/test-doubles 

• Building a scalable, modularized, testable app from scratch • https://developer.android.com/topic/architecture • https://developer.android.com/topic/modularization • https://developer.android.com/topic/modularization/patterns • https://developer.android.com/training/testing/fundamentals/ test-doubles • https://github.com/android/nowinandroid References