onPreviewKeyEvent

Compose Modifier

Common

fun Modifier.onPreviewKeyEvent(onPreviewKeyEvent: (KeyEvent) -> Boolean): Modifier

Adding this modifier to the modifier parameter of a component will allow it to intercept hardware key events when it (or one of its children) is focused.

Parameters

onPreviewKeyEvent This callback is invoked when the user interacts with the hardware keyboard. It gives ancestors of a focused component the chance to intercept a KeyEvent. Return true to stop propagation of this event. If you return false, the key event will be sent to this onPreviewKeyEvent's child. If none of the children consume the event, it will be sent back up to the root KeyInputModifierNode using the onKeyEvent callback.


onPreviewKeyEvent	This callback is invoked when the user interacts with the hardware keyboard. It gives ancestors of a focused component the chance to intercept a `KeyEvent`. Return true to stop propagation of this event. If you return false, the key event will be sent to this `onPreviewKeyEvent`'s child. If none of the children consume the event, it will be sent back up to the root `KeyInputModifierNode` using the onKeyEvent callback.

Code Examples

KeyEventSample

@Suppress("UNUSED_ANONYMOUS_PARAMETER")
@Composable
fun KeyEventSample() {
    // When the inner Box is focused, and the user presses a key, the key goes down the hierarchy
    // and then back up to the parent. At any stage you can stop the propagation by returning
    // true to indicate that you consumed the event.
    Box(Modifier.onPreviewKeyEvent { keyEvent1 -> false }.onKeyEvent { keyEvent4 -> false }) {
        Box(
            Modifier.onPreviewKeyEvent { keyEvent2 -> false }
                .onKeyEvent { keyEvent3 -> false }
                .focusable()
        )
    }
}