indices

Returns an IntRange of the valid indices for the children of this view group.

This can be used for looping:

for (i in viewGroup.indices.reversed) {
  if (viewGroup[i] is SomeView) {
    viewGroup.removeViewAt(i)
  }
}

Or to determine if an index is valid:

if (2 in viewGroup.indices) {
  // Do something…
}