How to animate UISlider Handle like in Apple's Music App?

Question

I have a custom image as the handle for my UISlider, using the following code:

slider.setThumbImage(UIImage(named: "scrollerHandle")!, forState: .normal)

In the default music app on iOS, when you want to change the position of a song and you click on the music slider, the handle animates and gets bigger, then when you let it go it shrinks once again. How does one do this with a UISlider?

I greatly appreciate every body's help.

Image of the slider in the music app