Hello,
We first noticed this on iOS 15 beta 4, and it is also happening on beta 5: after presenting a Touch ID prompt in our iOS app (and a fresh demonstration UIKit app) on an iPhone or iPad device with Touch ID enabled and running iOS 15 beta, about two minutes later we receive an additional UIApplicationWillResignNotification while the application is still active. It then happens again, another ~2 minutes later. As a result, any application that uses this notification to prepare for state restoration or to conceal or lock the UI will interrupt the user to prepare for resigning active, while the application is still active, two minutes after prompting the user for Touch ID authentication.
I have filed a report in Feedback Assistant (FB9457094), but I thought I would post here as well in case anybody else is seeing the same behavior and has a work-around. Feedback Assistant tells me there are currently no other similar reports.
Sample project to show the bug: https://github.com/billymeltdown/resign-active-test/
The SceneDelegate logs a message when the application resigns active. When the Touch ID prompt is presented, the app resigns active as expected, that's not a bug. Then wait two minutes -- it will happen again! (And then again, two minutes after that.)
(Not demonstrable on Simulator -- so far I've only seen the bug after prompting for Touch ID which requires running on a Touch ID enabled device.)
