Questions regarding 'Improving CollectionView Scrolling'

[F-Goncalves]

Hey @brminnick
I read your blog post about improving collection view scrolling and noticed that in your DataTemplateSelector you are creating a new instance of your DataTemplate whenever OnSelectTemplate is called.
However, the Xamarin documentation for DataTemplateSelectors explicitly states:

The DataTemplateSelector subclass must not return new instances of a DataTemplate on each call. Instead, the same instance must be returned. Failure to do so will create a memory leak and will disable virtualization.

Have you seen any evidence of this being the case for the GitTrends-App? I am considering your approach to improving CollectionView scrolling in my app, but stumbled upon above statement.

[TheCodeTraveler]

Oh! You may have just discovered the missing link!

I still see some occasional stuttering when scrolling on Android, albeit is better than the out-of-the box implementation, and I could never figure out why. This may be it!

I'll play around with this a bit and let you know what I find!

[TheCodeTraveler]

I just found an interesting work-around here.

I haven't tried it yet, but wanted to share it here so that I don't lose track of it: https://gist.github.com/jedusei/e15f45e1ae385d8b57413c168d3ef730

[F-Goncalves]

Interesting find, thanks for sharing.
It would be interesting to see if it would also be applicable to other platforms. Since the memory leak statement is not platform specific and the approach you shared is Android specific.

[TheCodeTraveler]

Confirmed that we should be reusing DataTemplates. You're a genius!

Not re-using DataTemplates causes a ton of memory allocation which leads to a ton of garbage collection (especially on Android).

Merging the updates in this PR: #552

[F-Goncalves]

Awesome, glad I could help.

Just to confirm: Did you actually notice a performance improvement with these changes?

[TheCodeTraveler]

Yes, huge performance improvement