SnapLayoutInfoProvider

Function

Common

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

A SnapLayoutInfoProvider for LazyLists.

Parameters


lazyListState	The `LazyListState` with information about the current state of the list
snapPosition	The desired positioning of the snapped item within the main layout. This position should be considered with regard to the start edge of the item and the placement within the viewport.

Returns


	A `SnapLayoutInfoProvider` that can be used with `snapFlingBehavior`

Common

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.sumOf {
                        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


lazyGridState	The `LazyGridState` with information about the current state of the grid
snapPosition	The desired positioning of the snapped item within the main layout. This position should be considered with regards to the start edge of the item and the placement within the viewport.

Returns


	A `SnapLayoutInfoProvider` that can be used with `snapFlingBehavior`