SnapLayoutInfoProvider

fun SnapLayoutInfoProvider(
    lazyListState: LazyListState,
    snapPosition: SnapPosition = SnapPosition.Center,
): SnapLayoutInfoProvider

A SnapLayoutInfoProvider for LazyLists.

Parameters

Returns

fun SnapLayoutInfoProvider(
lazyGridState: LazyGridState,
snapPosition: SnapPosition = SnapPosition.Center,
) =
object : SnapLayoutInfoProvider {
private val layoutInfo: LazyGridLayoutInfo
    get() = lazyGridState.layoutInfo

private val averageItemSize: Int
    get() {
        val layoutInfo = layoutInfo
        return if (layoutInfo.visibleItemsInfo.isEmpty()) {
            0
        } else {
            val numberOfItems = layoutInfo.visibleItemsInfo.size
            layoutInfo.visibleItemsInfo.fastSumBy {
                it.sizeOnMainAxis(layoutInfo.orientation)
            } / numberOfItems
        }
    }

override fun calculateApproachOffset(velocity: Float, decayOffset: Float): Float {
    return (decayOffset.absoluteValue - averageItemSize).coerceAtLeast(0.0f) *
        decayOffset.sign
}

override fun calculateSnapOffset(velocity: Float): Float {
    var distanceFromItemBeforeTarget = Float.NEGATIVE_INFINITY
    var distanceFromItemAfterTarget = Float.POSITIVE_INFINITY

    layoutInfo.visibleItemsInfo.fastForEach { item ->
        val distance =
            calculateDistanceToDesiredSnapPosition(
                mainAxisViewPortSize = layoutInfo.singleAxisViewportSize,
                beforeContentPadding = layoutInfo.beforeContentPadding,
                afterContentPadding = layoutInfo.afterContentPadding,
                itemSize = item.sizeOnMainAxis(orientation = layoutInfo.orientation),
                itemOffset = item.offsetOnMainAxis(orientation = layoutInfo.orientation),
                itemIndex = item.index,
                snapPosition = snapPosition,
                itemCount = layoutInfo.totalItemsCount,
            )

        if (distance <= 0 && distance > distanceFromItemBeforeTarget) {
            distanceFromItemBeforeTarget = distance
        }

        if (distance >= 0 && distance < distanceFromItemAfterTarget) {
            distanceFromItemAfterTarget = distance
        }
    }

    return calculateFinalOffset(
        with(lazyGridState.density) { calculateFinalSnappingItem(velocity) },
        distanceFromItemBeforeTarget,
        distanceFromItemAfterTarget,
    )
}
}

A SnapLayoutInfoProvider for LazyGrids.

Parameters

Returns