Android Academy · Lesson

Feature and Core Modules

Draw module boundaries.

Two Kinds of Modules

Most modularized Android apps organize code into two main kinds of modules: feature modules and core modules, plus a thin :app module on top.

Feature modules hold a user-facing slice of the app (a screen or flow).
Core modules hold shared infrastructure used by many features.

In this lesson you will learn how to draw these boundaries well.

Anatomy of a Feature Module

A feature module like :feature:profile contains everything a single feature needs: its Compose screens, its ViewModel, and its UI state. It is vertical: it owns the full slice from UI down to its view-model.

It depends on core modules for shared pieces, but it should not depend on other feature modules.

// feature/profile/ProfileScreen.kt
@Composable
fun ProfileScreen(viewModel: ProfileViewModel = hiltViewModel()) {
    val state by viewModel.uiState.collectAsStateWithLifecycle()
    when (state) {
        is ProfileUiState.Loading -> CircularProgressIndicator()
        is ProfileUiState.Success -> ProfileContent((state as ProfileUiState.Success).user)
        is ProfileUiState.Error -> ErrorMessage()
    }
}

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