method indexChanged

Source

bool indexChanged(key) {
  // If key isn't an int, or before the index, then it wasn't changed.
  if (key is! int || key < index) return false;

  // If this was a shift operation, anything after index is changed.
  if (addedCount != removed.length) return true;

  // Otherwise, anything in the update range was changed.
  return key < index + addedCount;
}