LazyLayoutScrollScope


A ScrollScope to allow customization of scroll sessions in LazyLayouts. This scope contains additional information to perform a custom scroll session in a scrollable LazyLayout.

For implementations for the most common layouts see:

Summary

Public functions

Int
calculateDistanceTo(targetIndex: Int, targetOffset: Int)

The "expected" distance to targetIndex.

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Unit
snapToItem(index: Int, offset: Int)

Immediately scroll to index and settle in offset.

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Public properties

Int

The index of the first visible item in the lazy layout.

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Int

The offset of the first visible item.

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Int

The total item count.

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Int

The last visible item in the LazyLayout, lastVisibleItemIndex - firstVisibleItemOffset + 1 is the number of visible items.

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Inherited functions

From androidx.compose.foundation.gestures.ScrollScope
Float
scrollBy(pixels: Float)

Attempts to scroll forward by pixels px.

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Public functions

calculateDistanceTo

fun calculateDistanceTo(targetIndex: Int, targetOffset: Int = 0): Int

The "expected" distance to targetIndex. This means the "expected" offset of targetIndex in the layout. In a LazyLayout, non-visible items don't have an actual offset, so this method should return an approximation of the scroll offset to targetIndex. If targetIndex is visible, then an "exact" offset should be provided.

Parameters
targetIndex: Int

The index position with respect to which this calculation should be done.

targetOffset: Int = 0

The offset with respect to which this calculation should be done.

Returns
Int

The expected distance to scroll so targetIndex is the firstVisibleItemIndex with targetOffset as the firstVisibleItemScrollOffset.

snapToItem

fun snapToItem(index: Int, offset: Int = 0): Unit

Immediately scroll to index and settle in offset.

Parameters
index: Int

The position index where we should immediately snap to.

offset: Int = 0

The offset where we should immediately snap to.

Public properties

firstVisibleItemIndex

val firstVisibleItemIndexInt

The index of the first visible item in the lazy layout.

firstVisibleItemScrollOffset

val firstVisibleItemScrollOffsetInt

The offset of the first visible item.

itemCount

val itemCountInt

The total item count.

lastVisibleItemIndex

val lastVisibleItemIndexInt

The last visible item in the LazyLayout, lastVisibleItemIndex - firstVisibleItemOffset + 1 is the number of visible items.