Java Android Clean Architecture & Modularization

Instructions

When designing or refactoring a Java-based Android app, follow Clean Architecture principles. Dependencies must flow inwards toward pure Java domain code. The repository standard is Java 17 with AndroidX + Hilt.

1. High-Level Layers

• Presentation Layer
  • Responsibility: Rendering views and handling user input.
  • Components: Activity, Fragment, ViewModel (Jetpack), LiveData, adapters.
  • Dependencies: Domain interfaces only (UseCases or repository interfaces).
• Domain Layer (Pure Java)
  • Responsibility: Business rules and domain entities.
  • Components: UseCases (e.g. GetArticles), immutable entities (prefer records), repository interfaces.
  • Rule: MUST NOT import android.* or androidx.*. Keep under :domain module or com.example.app.domain.
• Data Layer
  • Responsibility: Fetching, caching, and persisting data.
  • Components: Repository implementations, Retrofit services, Room DAOs, DTOs + mappers.