Changes

Take, for example, a UIView with a UIButton subview. If the user touches the screen over the button then the button, as first responder, will receive the event. If the button is unable to handle the event it will need to be passed up to the view object. If the view is also unable to handle the event it would then be passed to the view controller and so on.

When working with the responder chain, it is important to note that the passing of an event from one responder to the next responder in the chain does not happen automatically. If an event needs to be passed to the next responder, code must be written to make it happen.

A new feature introduced as part of the iOS 9 SDK is touch prediction. Each time the system updates the current coordinates of a touch on the screen, a set of algorithms attempt to predict the coordinates of the next location. A finger sweeping across the screen, for example, will trigger multiple calls to the touchesMoved method passing through the current touch coordinates. Also passed through to the method is a UIEvent object on which a method named predictedTouchesForTouch may be called, passing through the touch object representing the current location. In return, the method will provide an array of UITouch objects that predict the next few locations of the touch motion. This information can then be used to improve the performance and responsiveness of the app to the touch behavior of the user.

== Touch Coalescing ==