implementing-android-code

Extend BaseViewModel with State, Event, and Action types, annotate with @HiltViewModel, and make the state a @Parcelize data class. Implement handleAction synchronously, post internal actions from coroutines via sendAction, and persist state to SavedStateHandle for process death recovery.

Define a @Serializable route data class, an Args helper extracted from SavedStateHandle via toRoute, a NavController.navigateTo extension, and a NavGraphBuilder destination using composableWithSlideTransitions. This avoids string-based navigation and gives compile-time parameter safety.

Direct mutableStateFlow updates inside coroutines break the synchronous dispatch contract of the State-Action-Event pattern. Instead, coroutines should post internal actions with sendAction, and state updates happen only inside handleAction.

Use @EncryptedPreferences for credentials, tokens, and keys, and @UnencryptedPreferences for UI state and non-sensitive preferences. Disk sources extend BaseEncryptedDiskSource, which exposes putEncryptedString and putBoolean helpers for each store.

Extend BaseViewModelTest, mock repository interfaces with MockK using coEvery for suspend functions, and run tests with runTest. Assert state and events with Turbine's test block or the stateEventFlow helper, and inject a fixed Clock for time-dependent logic.

Common mistakes include injecting implementation classes instead of interfaces, throwing exceptions instead of returning domain-specific sealed result classes, and leaking implementation details into interface KDoc. Repositories should aggregate data sources and managers and expose StateFlow for observed data.