Programming iOS 6, 3rd Edition

Restricting Touches

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 UIView properties also restrict the delivery of touches to particular views:

userInteractionEnabled

If set to NO, this view (along with its subviews) is excluded from receiving touches. Touches on this view or one of its subviews “fall through” to a view behind it.

opacity

If set to 0.0 (or extremely close to it), this view (along with its subviews) is excluded from receiving touches. Touches on this view or one of its subviews “fall through” to a view behind it.

hidden

If set to YES, this view (along with its subviews) is excluded from receiving touches. This makes sense, since from the user’s standpoint, the view and its subviews are not even present.

multipleTouchEnabled

If set to NO, this view never receives more than one touch simultaneously; once it receives a touch, it doesn’t receive any other touches until that first touch has ended.

exclusiveTouch

This is the only one of these properties that can’t be set in the nib. An exclusiveTouch view receives a touch only if no other views ...