title: iOS Swift detect keyboard events
body: <p>Can I somehow detect events from iOS keyboard? </p>
  
  <p>I would like to detect this kind of events on the <code>UIViewController</code> which does not have <code>UITextField</code> or any sort of this kind of objects. </p>
  
  <p>All I have are four circles that are <code>UIView</code> and I would like to paint them in different colour when the button on the keyboard is pressed.</p>
  
  <p><a href="https://i.stack.imgur.com/KESpU.png" rel="noreferrer"><img src="https://i.stack.imgur.com/KESpU.png" alt="enter image description here"></a></p>