Drop-Down opens very slowly after one of the last items has been selected in a large list (2500 entries) about dropdown_button2

[wkolov]

I have tried it and the performance looks very good now. Thanks.

[wkolov]

Are there any news regarding this issue? It's actually a serious problem since meanwhile we have up to 5000 entries in the drop-down list and customers complain loudly about miserable performance. It seams to be an issue in browsers (tested with Chrome and Safari). The performance in mobile apps is much better even with large lists.

[AhmedLSayed9]

Sorry for the late response.
I'll check it this weekend and see if there's something we can do.

[AhmedLSayed9]

@wkolov Do you experience a delay if the selected item is at the beginning of the list or only in case it's far from start?

I was able to re-produce it using flutter's DropdownButton too.

[wkolov]

@AhmedLSayed9 This gets worse the further it gets from the beginning. DropdownButton is affected too, but it's not that slow (I measured 10 vs 17 seconds in my test setup). The issue is somewhat hard to catch. It seems to depend on the amount of free memory in the system and all the profiling tools I tried to use don't show anything helpful or even crash. I have found another searchable dropdown: https://pub.dev/packages/dropdown_search. It doesn't scroll to the selected item when the drop-down list opens and thus it is always quick.

[AhmedLSayed9]

@AhmedLSayed9 This gets worse the further it gets from the beginning. DropdownButton is affected too, but it's not that slow (I measured 10 vs 17 seconds in my test setup). The issue is somewhat hard to catch. It seems to depend on the amount of free memory in the system and all the profiling tools I tried to use don't show anything helpful or even crash. I have found another searchable dropdown: https://pub.dev/packages/dropdown_search. It doesn't scroll to the selected item when the drop-down list opens and thus it is always quick.

Well, the issue is scrolling over a very big list without specifying itemExtent causes janky performance.
We need to somehow set itemExtent, I'll look into it.

[AhmedLSayed9]

A fix is incoming. You'll be able to scroll fast even with different items length & separators:

Screen.Recording.2024-05-16.at.3.51.34.AM.mov

Note: the min supported flutter version will be increased to 3.16.0 and you'll have to not use intrinsicHeight: true of DropdownItem "which is false by default".

[AhmedLSayed9]

3.0.0-beta.14 is released, give it a try :)