onRotaryScrollEvent

fun Modifier.onRotaryScrollEvent(onRotaryScrollEvent: (RotaryScrollEvent) -> Boolean): Modifier

Adding this modifier to the modifier parameter of a component will allow it to intercept RotaryScrollEvents if it (or one of its children) is focused.

Here is an example of a scrollable container that scrolls in response to RotaryScrollEvents.

This sample demonstrates how a parent can add an onRotaryScrollEvent modifier to gain access to a RotaryScrollEvent when a child does not consume it:

Parameters

Returns

Code Examples

RotaryEventSample

@Composable
fun RotaryEventSample() {
    val scrollState = rememberScrollState()
    val coroutineScope = rememberCoroutineScope()
    val focusRequester = remember { FocusRequester() }
    Column(
        modifier =
            Modifier.fillMaxWidth()
                .verticalScroll(scrollState)
                .onRotaryScrollEvent {
                    coroutineScope.launch {
                        scrollState.scrollTo(
                            (scrollState.value + it.verticalScrollPixels).roundToInt()
                        )
                    }
                    true
                }
                .focusRequester(focusRequester)
                .focusable()
    ) {
        repeat(100) {
            Text(text = "item $it", modifier = Modifier.align(CenterHorizontally), color = White)
        }
    }
    LaunchedEffect(Unit) { focusRequester.requestFocus() }
}

PreRotaryEventSample

@Composable
fun PreRotaryEventSample() {
    MaterialTheme(colors = darkColors()) {
        val rowScrollState = rememberScrollState()
        val columnScrollState = rememberScrollState()
        val coroutineScope = rememberCoroutineScope()
        val focusRequester = remember { FocusRequester() }
        var interceptScroll by remember { mutableStateOf(false) }
        Column(
            Modifier.onPreRotaryScrollEvent {
                    // You can intercept an event before it is sent to the child.
                    if (interceptScroll) {
                        coroutineScope.launch { rowScrollState.scrollBy(it.horizontalScrollPixels) }
                        // return true to consume this event.
                        true
                    } else {
                        // return false to ignore this event and continue propagation to the child.
                        false
                    }
                }
                .onRotaryScrollEvent {
                    // If the child does not use the scroll, we get notified here.
                    coroutineScope.launch { rowScrollState.scrollBy(it.horizontalScrollPixels) }
                    true
                }
        ) {
            Row(
                modifier = Modifier.align(CenterHorizontally),
                verticalAlignment = CenterVertically,
            ) {
                Text(
                    modifier = Modifier.width(70.dp),
                    text = if (interceptScroll) "Row" else "Column",
                    style = TextStyle(color = White),
                )
                Switch(checked = interceptScroll, onCheckedChange = { interceptScroll = it })
            }
            Row(modifier = Modifier.fillMaxWidth().horizontalScroll(rowScrollState)) {
                repeat(100) {
                    Text(
                        text = "row item $it ",
                        modifier = Modifier.align(CenterVertically),
                        color = White,
                    )
                }
            }
            Column(
                modifier =
                    Modifier.fillMaxWidth()
                        .verticalScroll(columnScrollState)
                        .onRotaryScrollEvent {
                            coroutineScope.launch {
                                columnScrollState.scrollBy(it.verticalScrollPixels)
                            }
                            true
                        }
                        .focusRequester(focusRequester)
                        .focusable()
            ) {
                repeat(100) {
                    Text(
                        text = "column item $it",
                        modifier = Modifier.align(CenterHorizontally),
                        color = White,
                    )
                }
            }
        }
        LaunchedEffect(Unit) { focusRequester.requestFocus() }
    }
}