Returns a Boolean value indicating whether this object is the first responder.
YES if the receiver is the first responder or
NO if it is not.
UIKit dispatches some types of events, such as motion events, to the first responder initially.
Managing the Responder Chain
Returns the next responder in the responder chain, or
nil if there is no next responder.
Returns a Boolean value indicating whether the receiver is willing to relinquish first-responder status.
Notifies this object that it has been asked to relinquish its status as first responder in its window.