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@Composable | |
fun InputValidationScreen(viewModel: InputValidationAutoViewModel = hiltViewModel()) { | |
val events = remember(viewModel.events, lifecycleOwner) {..} | |
val name by viewModel.name.collectAsStateWithLifecycle() | |
val creditCardNumber by viewModel.creditCardNumber.collectAsStateWithLifecycle() | |
val areInputsValid by viewModel.areInputsValid.collectAsStateWithLifecycle() | |
LaunchedEffect(Unit) { | |
events.collect { event -> |
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handle[NAME] = name.value.copy(value = input, errorId = errorId) |
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@Parcelize | |
data class InputWrapper( | |
val value: String = "", | |
val errorId: Int? = null | |
) : Parcelable |
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fun <T> SavedStateHandle.getStateFlow( | |
scope: CoroutineScope, | |
key: String, | |
initialValue: T | |
): MutableStateFlow<T> { | |
val liveData = getLiveData(key, initialValue) | |
val stateFlow = MutableStateFlow(initialValue) | |
val observer = Observer<T> { value -> if (value != stateFlow.value) stateFlow.value = value } | |
liveData.observeForever(observer) |
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object InputValidator { | |
fun getNameErrorIdOrNull(input: String): Int? { | |
return when { | |
input.length < 2 -> R.string.name_too_short | |
//ideally provide different error messages for different errors | |
else -> null | |
} | |
} |
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@HiltViewModel | |
class InputValidationAutoViewModel @Inject constructor( | |
private val savedStateHandle: SavedStateHandle | |
) : ViewModel() { | |
val name = handle.getStateFlow(NAME, InputWrapper()) | |
val creditCardNumber = handle.getStateFlow(CREDIT_CARD_NUMBER, InputWrapper()) | |
val areInputsValid = combine(name, creditCardNumber) { name, cardNumber -> | |
name.value.isNotEmpty() && name.errorId == null && cardNumber.value.isNotEmpty() && cardNumber.errorId == null | |
}.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000L), false) |
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@Composable | |
fun LifecycleAwareCurrencyPriceCard( | |
currencyPrice: CurrencyPrice, | |
currencyPriceUpdateFlow: Flow<Int>, | |
onCurrencyUpdated: (progress: Int) -> Unit, | |
onDisposed: () -> Unit, | |
) { | |
val lifecycleOwner = LocalLifecycleOwner.current | |
val lifecycleAwareCurrencyPriceFlow = remember(currencyPriceUpdateFlow, lifecycleOwner) { | |
currencyPriceUpdateFlow.flowWithLifecycle(lifecycleOwner.lifecycle, Lifecycle.State.STARTED) |
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@Composable | |
fun LifecycleAwareCurrenciesScreen(viewModel: LifecycleAwareCurrenciesViewModel) { | |
val currencyPrices by viewModel.currencyPrices.collectAsStateWithLifecycle() | |
LazyColumn { | |
itemsIndexed(currencyPrices, { _, item -> item.id }) { index, currencyPrice -> | |
LifecycleAwareCurrencyPriceCard( | |
currencyPrice = currencyPrice, | |
currencyPriceUpdateFlow = viewModel.provideCurrencyUpdateFlow(), | |
onDisposed = { viewModel.onDisposed(index) }, | |
onCurrencyUpdated = { newPrice -> viewModel.onCurrencyUpdated(newPrice, index) }) |
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class LifecycleAwareCurrenciesViewModel : ViewModel() { | |
private val _currencyPrices = MutableStateFlow(listOf<CurrencyPrice>()) | |
val currencyPrices: StateFlow<List<CurrencyPrice>> get() = _currencyPrices | |
init { | |
getCurrencyPrices() | |
} | |
private fun getCurrencyPrices() {} //same as before |
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private suspend fun observePriceUpdateFlow(index: Int, currencyPriceUpdateFlow: Flow<Int>) { | |
currencyPriceUpdateFlow.collect { newPrice -> | |
val newFluctuation = when { | |
newPrice > _currencyPrices.value[index].price -> PriceFluctuation.UP | |
else -> PriceFluctuation.DOWN | |
} | |
val updatedCurrencyPrice = _currencyPrices.value[index].copy( | |
price = newPrice, | |
priceFluctuation = newFluctuation | |
) |