---
title: "onPreRotaryScrollEvent"
description: "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.


When the user rotates the side button on a wear device, a [RotaryScrollEvent] is sent to the
focused item. Before reaching the focused item, this event starts at the root composable, and
propagates down the hierarchy towards the focused item. It invokes any [onPreRotaryScrollEvent]s
it encounters on ancestors of the focused item. After reaching the focused item, the event
propagates up the hierarchy back towards the parent. It invokes any [onRotaryScrollEvent]s it
encounters on its way back.

Return true to indicate that you consumed the event and want to stop propagation of this event."
type: "modifier"
---

<div class='type'>Compose Modifier</div>

<a id='references'></a>
<div class='sourceset sourceset-common'>Common</div>


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


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


When the user rotates the side button on a wear device, a `RotaryScrollEvent` is sent to the
focused item. Before reaching the focused item, this event starts at the root composable, and
propagates down the hierarchy towards the focused item. It invokes any `onPreRotaryScrollEvent`s
it encounters on ancestors of the focused item. After reaching the focused item, the event
propagates up the hierarchy back towards the parent. It invokes any `onRotaryScrollEvent`s it
encounters on its way back.

Return true to indicate that you consumed the event and want to stop propagation of this event.

#### Parameters

| | |
| --- | --- |
| 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`. |


#### Returns

| | |
| --- | --- |
|  | true if the event is consumed, false otherwise. |




## Code Examples
### PreRotaryEventSample
```kotlin
@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() }
    }
}
```