Objective

To describe the Android project structure which focuses on separation of concern, modularization, scalability & Testability.

Kindly Note: This is only a structural explanation. Here, it doesn’t cover detailed classes.

Project Structure (Modularization):

App Module: This is your main application module responsible for assembling the other modules and presenting the UI.
Core Module: Contains common code shared across modules (utilities, extensions, constants).
Data Module: Handles data access (network, database, repositories).
Domain Module: Contains business logic (use cases, interactors).
Feature Modules: Each feature (e.g., login, profile, settings) gets its own module.

Architectural Pattern (Separation of Concerns):

We’ll use Model-View-ViewModel (MVVM) for clear separation:
Model: Represents data and business logic (entities, repositories in the Data module, use cases in the Domain module).
View: UI components (Activities, Fragments, Composables in the Feature and App modules).
ViewModel: Connects the View and Model, prepares data for display, and handles user interactions (in the Feature modules).

Example: News App

Let’s imagine a simple news app with two features: “Top Headlines” and “Search News.”

1. Core Module (: core)
   NetworkUtils.kt: Helper functions for network calls.
   Constants.kt: API endpoints, keys, etc.
2. Data Module (:data)
   NewsRepository.kt:
   Fetches news data from a network API (using Retrofit).
   Caches data locally (using Room database).
   Provides a single source of truth for news data.
   NewsApi.kt: Retrofit interface for the news API.
   NewsDao.kt: Room DAO for accessing the local database.
3. Domain Module (:domain)
   GetTopHeadlinesUseCase. kt: Fetches top headlines from the repository.
   SearchNewsUseCase.kt: Searches for news based on a query, using the repository.
4. Feature Modules
   :feature:topheadlines
   TopHeadlinesViewModel. kt:
   Uses GetTopHeadlinesUseCase to fetch data.
   Exposes StateFlow for the UI to observe (list of news articles, loading state, errors).
   TopHeadlinesScreen.kt (Composable):
   Collects the StateFlow from the ViewModel.
   Displays the list of headlines.
   :feature:searchnews
   SearchNewsViewModel. kt:
   Uses SearchNewsUseCase to search for news.
   Exposes StateFlow for the UI.
   SearchNewsScreen.kt (Composable):
   Collects the StateFlow from the ViewModel.
   Provides a search bar and displays results.
5. App Module (:app)
   MainActivity.kt: Sets up navigation between the two feature screens.
   AppTheme.kt: Defines the app’s theme.
   Dependency Injection (Hilt):
   Use Hilt to provide dependencies:
   Annotate NewsRepository with @Singleton to provide a single instance.
   Inject GetTopHeadlinesUseCase and SearchNewsUseCase into their respective ViewModels.
   Explanation:
   Separation of Concerns: Each module has a clear responsibility, making the code maintainable and testable.
   Modularization: Features are isolated, allowing for independent development and potential reuse.
   Testability: Each layer can be tested in isolation (unit tests for use cases, UI tests for Composables).
   Remember:
   

This is a simplified example. Real projects might have more complex data handling, error management, and navigation.
Adapt this structure to your specific app’s needs.
By following these principles, you’ll create a well-structured Android project that’s easy to understand, maintain, and scale.

Thank you.