Sometimes, interruptions such as phone call occur and disturb a regular behavior of an app in iPhone or iPad. For example, I created one UIScrollView instance and implemented UIScrollView delegate methods: scrollViewWillBeginDragging and scrollViewDidEndDragging(and scrollViewDidEndDecelerating). A scrollViewWillBeginDragging method deactivated all custom buttons in my app. Then scrollViewDidEndDragging and scrollViewDidEndDecelerating methods activated these custom buttons. That is, while the user scrolled, all custom buttons became deactivated for a while. The problem was that while the user started to drag and just held an UIScrollView instance, if I took a screenshot by pressing a home button and a power button, then any of scrollViewDidEndDragging and scrollViewDidEndDecelerating didn't get called. So the app became messed up. I implemented a UIApplicationWillResignActiveNotification method in my UIViewController, but it didn't get called after taking a screenshot. How can I catch any kind of interruption that disturbs a regular flow of events? Sometimes, touchesEnd and touchesCanceled didn't get called too due to an interruption. Thank you.