onPreRotaryScrollEvent

Modifier in Compose Ui

Adding this [modifier][Modifier] to the [modifier][Modifier] parameter of a component will allow it to intercept [RotaryScrollEvent]s if it (or one of its children) is focused.

Last updated: 2024-10-22 13:47

Installation

dependencies {
   implementation("androidx.compose.ui:ui:1.8.0-alpha04")
}

Overloads

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

Parameters

name

description

onPreRotaryScrollEvent

This callback is invoked when the user interacts with the rotary button on a wear device. It gives ancestors of a focused component the chance to intercept a [RotaryScrollEvent].When the user rotates the side button on a wear device, a [RotaryScrollEvent] is sent to thefocused item. Before reaching the focused item, this event starts at the root composable, andpropagates down the hierarchy towards the focused item. It invokes any [onPreRotaryScrollEvent]sit encounters on ancestors of the focused item. After reaching the focused item, the eventpropagates up the hierarchy back towards the parent. It invokes any [onRotaryScrollEvent]s itencounters on its way back.Return true to indicate that you consumed the event and want to stop propagation of this event.

Code Example

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() }
    }
}