isRevealed method

bool isRevealed(int index, { required ScrollExtent scrollExtent, VisibilityStrategy strategy = VisibilityStrategy.tolerance, double tolerance = 0.1, bool shouldNormalized = true, bool shouldConvert = false, })

if index is revealed in its closest ancestor RenderSliver. typically, index must have been observed before checking isRevealed.

strategy is used to determine the threshold of which index should be regarded as revealed/visible.

shouldNormalized indicates if we need to normalizeIndex into a valid range.

ScrollExtent is the current scroll extent built from ScrollPosition to indicate the current min/max scroll extent and pixels.

if shouldConvert is true, it would try to use targetToRenderIndex to convert index to its render index. shouldConvert is always false when using internally for jumpToIndex and animateToIndex.

Note that isRevealed should only be used when firstLayoutFinished is completed and isActive

Implementation

bool isRevealed(
  int index, {
  required ScrollExtent scrollExtent,
  VisibilityStrategy strategy = VisibilityStrategy.tolerance,
  double tolerance = 0.1,
  bool shouldNormalized = true,
  bool shouldConvert = false,
}) {
  assert(isActive && firstLayoutFinished);

  index = shouldConvert ? targetToRenderIndex?.call(index) ?? index : index;

  final validIndex = shouldNormalized ? normalizeIndex(index) : index;

  final itemScrollExtent = getItemScrollExtent(validIndex);
  final itemSize = getItemSize(validIndex);

  if (!renderVisible || itemScrollExtent == null || itemSize == null) {
    return false;
  }

  final leadingOffset = itemScrollExtent.getLeadingOffset(origin!.offset);

  final double trailingOffset = itemScrollExtent.getTrailingOffset(
    leadingOffset,
    axis: axis,
    size: itemSize,
  );

  final trailingEdge = getTrailingEdgeFromScroll(scrollExtent);

  return strategy.handle(
    leadingOffset,
    trailingOffset,
    leadingEdge: scrollExtent.current,
    trailingEdge: trailingEdge,
    maxScrollExtent: scrollExtent.max,
    tolerance: tolerance,
  );
}