Returns a Boolean value indicating whether this object can become the first responder.
YES if the receiver can become the first responder or
NO if it cannot.
This method returns
NO by default. Subclasses must override this method and return
YES to be able to become first responder.
Do not call this method on a view that is not currently in the active view hierarchy. The result is undefined.
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 this object is the first 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.