iOS Face ID/Touch ID Lock Screen Conflict in willEnterForegroundNotification - ios

Question

I have code that puts a blurred UIVisualEffectView over the current window when the didEnterBackgroundNotification notification is fired. It then tries to reverse this when willEnterForegroundNotification is fired (simplified for easy reading):
class AutoBlur {
init() {
NotificationCenter.default.addObserver(self, selector: #selector(appDidEnterBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(appWillEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)
}
#objc func appDidEnterBackground() {
blur()
}
#objc func appWillEnterForeground() {
guard UserState.isScreenLockEnabled else {
unblur()
return
}
let authContext = LAContext()
authContext.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "test") { success, error in
DispatchQueue.main.async {
guard success else {
return
}
unblur()
}
}
}
//...
}
While this approach generally works, when testing the Face ID functionality of app I found the following anomaly:
Open the app
Turn the screen off on the device
Wake the device
Swipe up on the device's lock-screen
Expected results: The device should unlock, and then my app should run its Face ID evaluate code to un-blur the view.
Actual results: The swipe-up action is undercut by my app's Face ID evaluation code. It prevents the user from being able to swipe up on their lock-screen, effectively locking them out of their device.
Is there some state I should be monitoring or some other event that's safer to respond to for triggering my Face ID evaluation?