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Multiple SliverChildBuilderDelegates always build the first child #95028
Description
From discussion in #26072, this Dartpad shows that the first item in every SliverList (using a lazy SliverChildBuilderDelegate) is built regardless of whether it is visible in the viewport.
This is significantly better than using shrinkwrap 💀 but it is still not as expected.
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! Doctor found issues in 1 category.
Activity
Piinks commentedon Jan 31, 2022
After doing some digging, I have found that this is intentional behavior. Currently, we must layout at least one child in order to estimate the maximum scroll offset. We should update the documentation to better explain this, and maybe also include some example code showing how one could override the way maxScrollExtent is estimated for SliverLists and SliverGrids.
davidmartos96 commentedon Feb 3, 2022
@Piinks Happy to see this moving forward.
Knowing the problem now, is there any example on how we can achieve the "deadly" Dartpad above in a performant way?
Piinks commentedon Feb 15, 2022
Currently, the above dartpad is the most performant for that composition, it is certainly a lot better than shrinkwrap. There are a lot of ways to compose widgets though, so there could be another way that I haven't thought of.
I filed #97676 to look into different methods for estimating the max scroll offset without requiring at least one child be built. I would follow up there if you are interested. :)
github-actions commentedon Mar 1, 2022
This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of
flutter doctor -vand a minimal reproduction of the issue.