IOS Swift: display activity indicator while image is loading from web

I am trying to implement something in Swift that when a view is loaded, it displays the network activity indicator briefly while loading an image from the web.

I tried putting the code in viewDidLoad() but of course, there's a delay while segueing from the previous controller until the image file is fully loaded before it displays.

How would I load a blank page and display the indicator while the image is being loaded from the web?