应用程序处于后台时，可以看到UILocalNotification Banner

I'm working on a VoIP phone for iOS, and if a call comes in while running in the background, I do a presentLocalNotificationNow with a UILocalNotification message to inform the user. This works fine, however the banner expires and rolls off the screen before the user has enough of a chance to swipe and answer. I have tried scheduling further notifications at regular intervals, but that fills up the notification centre and causes the banner to appear to be tumbling.I'm working on a VoIP phone for iOS, and if a c