Bug 40922 - ListView ItemAppearing Fires on Every Row On Each Add
Summary: ListView ItemAppearing Fires on Every Row On Each Add
Status: RESOLVED FIXED
Alias: None
Product: Forms
Classification: Xamarin
Component: Windows ()
Version: 2.2.0
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Paul DiPietro [MSFT]
URL:
Depends on:
Blocks:
 
Reported: 2016-05-05 22:30 UTC by Ray Kelly
Modified: 2017-06-19 17:50 UTC (History)
3 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

Notice (2018-05-24): bugzilla.xamarin.com is now in read-only mode.

Please join us on Visual Studio Developer Community and in the Xamarin and Mono organizations on GitHub to continue tracking issues. Bugzilla will remain available for reference in read-only mode. We will continue to work on open Bugzilla bugs, copy them to the new locations as needed for follow-up, and add the new items under Related Links.

Our sincere thanks to everyone who has contributed on this bug tracker over the years. Thanks also for your understanding as we make these adjustments and improvements for the future.


Please create a new report on Developer Community or GitHub with your current version information, steps to reproduce, and relevant error messages or log files if you are hitting an issue that looks similar to this resolved bug and you do not yet see a matching new report.

Related Links:
Status:
RESOLVED FIXED

Description Ray Kelly 2016-05-05 22:30:36 UTC
When a ListView is bound to an ObservableCollection, adding an object causes ItemAppearing to fire once for every item regardless if its already shown or not.

For instance.  

List View Items 1
IteamAppearig fires once

Add 1 item to collection
IteamAppearing fires twice

Add 1 item to collection
IteamAppearing 3 times

Add 1 item to collection
IteamAppearing 4 times
etc........

This may only happen if unevenrows set to true.
Comment 1 Paul DiPietro [MSFT] 2016-06-14 20:48:35 UTC
We'd be happy to help you resolve this issue. Please help us by attaching a reduced reproduction to the bug by starting with a clean Xamarin.Forms project and adding just the code necessary to demonstrate the issue. If you'd do this for us we would very much appreciate it. If you are able to reproduce the issue without modifying the platform specific projects that would eliminate a number of possibilities and likely expedite a resolution. 

Warm regards,
Xamarin Forms Team
Comment 2 Ray Kelly 2016-09-12 17:51:19 UTC
I believe this is related to this bug

https://bugzilla.xamarin.com/show_bug.cgi?id=43313

As you "scrollto" to the bottom, it fires the ItemAppearing for every row (like 1000) and the screen flickers as it scrolls top to bottom.
Comment 3 Paul DiPietro [MSFT] 2017-06-19 17:50:41 UTC
This issue will be closed as the referred to issue appears to have been resolved. Please reopen this and attach a minimized reproduction project if the issue still exists as of the latest prerelease or nightly build.

Thanks!