[Android] ItemTemplate count has exceeded the limit of 23. Please make sure to reuse DataTemplate objects

[leobragatti]

Description

Trying to use ListView and this error always happens
ItemTemplate count has exceeded the limit of 23. Please make sure to reuse DataTemplate objects

Steps to Reproduce

1. Just trying to use a ListView

Basic Information

• IDE: VisualStudio Community Mac 7.5.2 (build 40)

• Runtime:
  Mono 5.10.57
  Xamarin.Mac 4.4.1.178
  Xamarin.Android 8.3.3.2
  SDK Tools Version: 26.1.1
  SDK Platform Tools: 27.0.1
  SDK Build Tools: 27.0.3

• Platform Target Frameworks: use target framework version

  • Android: API Level 15

• Nuget Packages:
  Xamarin Forms 3.0.0.482510

• Affected Devices:
  Samsung SM-J500M (API 23)

[samhouts]

Hi @leobragatti! Android has a limitation of the number of cell types it can use in a single ListView. If you're not reusing your DataTemplates (i.e., you return a new DataTemplate for every list item), you'll run into this limitation quickly. Please make sure you're following the instructions in https://docs.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/templates/data-templates/. If you are still unable to proceed, please attach a small project that demonstrates the issue you're having. Thanks!

[jassmith]

Please re-open if you are still having issues after following Sams advice.

[leobragatti]

Thanks for the help @samhouts . I checked my code and I was using the TemplateSelector in a wrong way.

[billvenhaus]

@samhouts Do you know why a limit of 20 (23) was chosen in ListViewAdapter? I'm working on a rather large & complicated ListView that can return up to 35 unique DataTemplates in a DataTemplateSelector. I am a little curious. I haven't been able to find docs that the native Android ListView can't handle more types.

[samhouts]

@billvenhaus I don't believe that it was a limitation from Android itself but an arbitrary number that we selected and hoped would be sufficient for even the most complex ListViews. The limitation from Android was that they required us to define the exact number of ViewTypes that will be used (it can't be dynamically computed, like iOS or UWP allows), and it allocates that number in memory. We didn't want to select an exceptionally large number and impact performance when it wasn't necessary for most cases.