Explanation of CollapsingToolbarLayout

Question

In the design library, CollapsingToolbarLayout introduces some cool new effects.

1. How many children can CollapsingToolbarLayout have? Is there anything to keep in mind when adding additional children?
2. I've seen code online where AppBarLayout, CollapsingToolbarLayout, and CollapsingToolbarLayout's children have layout_scrollFlags set. Is there a reason for this? Where are the scroll flags supposed to go?

Note: I understand independently what each of the scroll flags do (scroll, enterAlways, etc.)

Answer 1

Saul Molinero explains it very thoroughly here.

Cheers