CODEWITHSUNDEEP
androidkotlincomposable
Sunbey13
Sunbey13

Reputation: 423

how to check if the Flow is empty?

I am passing data to render the list as a Flow<>. If it is empty, instead of the list, I need to display the inscription "No data". How can I set a condition to check if the flow is empty?

@Composable
fun HistoryLayout(viewModel: HistoryViewModel = viewModel()) {
    val historyFlow = viewModel.historyStateFlow.collectAsLifecycleState().value
    if (is historyFlow empty???) {
        Box(
            modifier = Modifier.fillMaxSize(),
            contentAlignment = Alignment.Center
        ) {
            Text(
                stringResource(R.string.emptylist),
                textAlign = TextAlign.Center,
                maxLines = MAX_LINES,
                overflow = TextOverflow.Ellipsis,
            )
        }

    } else {
        HistoryTableList(historyFlow = historyFlow)
    }
}

Upvotes: 0

Views: 2321

Answers (2)

Gijs Stokman
Gijs Stokman

Reputation: 173

A better way of handling this would be to call .firstOrNull() on the Flow. If there are no events emitted by the flow this will return null so you can check for that. If your flow emits an empty list the full check could be:

val hasItems = viewModel.historyStateFlow.firstOrNull()?.isNotEmpty() ?: false

Upvotes: 0

Sunbey13
Sunbey13

Reputation: 423

This trick helped me solve the problem, however i hope to still find a better solution From Flow i get LazyPagingItems<...>, which has *.itemCount method.

@Composable
fun HistoryLayout(viewModel: HistoryViewModel = viewModel()) {
    val historyFlow = viewModel.historyStateFlow.collectAsLifecycleState().value
    val historyItems: LazyPagingItems<HistoryRecordEntity> = historyFlow.collectAsLazyPagingItems()

    if (historyItems.itemCount == 0) {
        Box(
            modifier = Modifier.fillMaxSize(),
            contentAlignment = Alignment.Center
        ) {
            Text(
                stringResource(R.string.emptylist),
                textAlign = TextAlign.Center,
                maxLines = MAX_LINES,
                overflow = TextOverflow.Ellipsis,
            )
        }
    } else {
        HistoryTableList()
    }
}

Upvotes: 0

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