support nested scroll view

[edingroot]

Hi!

I did some small changes to support nested scroll view, i.e. scrollable parent with non-scrollable list view children. Also added a demo in the sample app.

Please kindly help to review and let me know if it is inappropriate, thank you!

Some related issues: #22 #23 #49 #89

[edingroot]

Hi @henrichen, Could you please kindly review my changes when you have time? Thanks :)

[MiniSuperDev]

Hi, I try your branch to create a bidirectional lazy load list like this https://github.com/quire-io/scroll-to-index/issues/89 The idea is use center key like flutter docs said https://github.com/flutter/flutter/blob/5464c5bac742001448fe4fc0597be939379f88ea/packages/flutter/lib/src/widgets/scroll_view.dart#L502-L513

I create a gist where you can enable a disable the center key, and you can see that only highlight work, but the scroll to not work when the center key is enable.

how can I keep the scroll to index behavior while have the center key? or maybe do you know other way to create a list that append items to the top of the list by preserving the scroll, the solution that I used is from https://github.com/flutter/flutter/issues/21541#issuecomment-629121578

thank you