Touch events can be turned off entirely at the application level with UIApplication’s
beginIgnoringInteractionEvents. It is quite common to do this during animations and other lengthy operations during which responding to a touch could cause undesirable results. This call should be balanced by
endIgnoringInteractionEvents. Pairs can be nested, in which case interactivity won’t be restored until the outermost
endIgnoringInteractionEvents has been reached.
A number of high-level UIView properties also restrict the delivery of touches to particular views:
0.0(or extremely close to it), this view (along with its subviews) is excluded from receiving touches.
exclusiveTouchview receives a touch only if no other views in the same window have touches associated with them; once an
exclusiveTouchview has received a touch, then while that touch exists no other view in the same window receives any touches.
A UIWindow ignores
multipleTouchEnabled; it always receives ...