computeMaxScrollOffset method

  1. @visibleForTesting
  2. @protected
double computeMaxScrollOffset(
  1. SliverConstraints constraints,
  2. @Deprecated('The itemExtent is already available within the scope of this function. ' 'This feature was deprecated after v3.20.0-7.0.pre.') double itemExtent
)

Called to obtain a precise measure of the total scrollable extents of this object.

Must return the precise total distance from the start of the child with the earliest possible index to the end of the child with the last possible index.

This is used when no child is available for the index corresponding to the current scroll offset, to determine the precise dimensions of the sliver. It must return a precise value. It will not be called if the childManager returns an infinite number of children for positive indices.

If itemExtentBuilder is null, multiplies the itemExtent by the number of children reported by RenderSliverBoxChildManager.childCount. If itemExtentBuilder is non-null, sum the extents of the first RenderSliverBoxChildManager.childCount children.

See also:

Implementation

@visibleForTesting
@protected
double computeMaxScrollOffset(
  SliverConstraints constraints,
  @Deprecated(
    'The itemExtent is already available within the scope of this function. '
    'This feature was deprecated after v3.20.0-7.0.pre.'
  )
  double itemExtent,
) {
  if (itemExtentBuilder == null) {
    itemExtent = this.itemExtent!;
    return childManager.childCount * itemExtent;
  } else {
    double offset = 0.0;
    double? itemExtent;
    for (int i = 0; i < childManager.childCount; i++) {
      itemExtent = itemExtentBuilder!(i, _currentLayoutDimensions);
      if (itemExtent == null) {
        break;
      }
      offset += itemExtent;
    }
    return offset;
  }
}