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name: android-state description: Configure ViewModel state emission with StateFlow, SharedFlow, and sealed UiState classes in Android. Use for state modeling and sharing policies; defer generic lifecycle collection, navigation-event plumbing, Hilt injection, test code, and configuration-change recipes to their specific skills. metadata: triggers: files: - '/*ViewModel.kt' - '/*UiState.kt' keywords: - viewmodel - stateflow - livedata - uistate - MutableStateFlow - collectAsState - viewModelScope - UiState

Android State Management

Priority: P0 (CRITICAL)

1. Structure ViewModel

• Expose ONE StateFlow<UiState> via .asStateFlow().
• Use viewModelScope for all coroutines.
• Trigger initial load in init block.

See templates for ViewModel and UiState examples.

2. Define UI State (LCE Pattern)

• Use sealed interface with Loading, Content, Error variants.
• Mark data classes @Immutable.

See templates for sealed UiState pattern.

3. Collect State Lifecycle-Safely

• Use collectAsStateWithLifecycle() in Compose.
• Use SharingStarted.WhileSubscribed(5000) for shared resources.

Anti-Patterns

• No LiveData for New Code: Use StateFlow — lifecycle-safe and Compose-compatible.
• No Public MutableStateFlow: Expose only .asStateFlow() to consumers.
• No Context in ViewModel: Leaks Activity. Use Application context if truly needed.

Verification

• Each ViewModel exposes exactly one StateFlow<UiState>.
• UiState is a sealed interface with Loading, Content, Error variants.
• UI collects with collectAsStateWithLifecycle().
• ./gradlew test passes for ViewModel tests.

References

• Templates