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Presentation Package

Presentation Package

The Presentation package manages the app's user interface (UI) and contains four sub-packages:

Components​

Contains reusable UI elements like the toolbar, loading indicators, and dialogs to maintain consistent design across the app.

Theme​

Manages the app's appearance, including colors, typography (fonts), and themes (dark/light theme), allowing easy customization of the app's visual style.

Holds every navigation destination, the back-stack model, the Navigator API, and the root AppNavigation composable. Feature folders intentionally don't contain navigation glue — see the dedicated Navigation page for the full picture.

Screens​

Contains all the screens in the app. Each screen folder follows a structured setup:

  • Screen: The main composable function for the UI.
  • UiState: Represents the current ui state of the screen, and also contains UiEvent to handle user actions and events on the screen.
  • UiStateHolder (ViewModel): Manages the screen's state. UiStateHolder is an abstract class extending ViewModel from androidx.lifecycle. It interacts with the UiState and handles events (UiEvent) triggered by user actions.

The route definitions and the wiring that connects each screen to the navigator (push targets, back behaviour, parameter passing) live in presentation/navigation/Routes.kt and AppNavigation.kt, not in the feature folder.

For new screens, extend the UiStateHolder class. When you need to call a suspend function, do so within the uiStateHolderScope.launch, which delegates to viewModelScope.

class NewUiStateHolder() : UiStateHolder() {
    fun testFunction() = uiStateHolderScope.launch {
        //Call suspend function
    }
}

To obtain a holder instance inside the entry<…> block in AppNavigation.kt, use the uiStateHolder helper:

entry<OnBoardingScreenRoute> {
    val holder = uiStateHolder<OnBoardingUiStateHolder>()
    OnBoardingScreen(uiStateHolder = holder, /* … */)
}

The Navigation 3 entry decorator scopes ViewModels to their NavEntry, so each holder lives as long as its destination is on the back stack and is cleared automatically when popped — no separate "navigator-scoped" helper needed.

Ensure that the DI setup is done in AppInitializer within the presentationModule, for example, by adding viewModelOf(::NewUiStateHolder) to handle dependencies for the new UiStateHolder.