Why is this Lottie JSON animation not showing in the UIView upon building?

Question

This is my UIViewController:

 import UIKit
 import Lottie

 class ViewController: UIViewController {
    
  override func viewDidLoad() {
      super.viewDidLoad() {
      let rocketAnimationView = AnimationView()
      //Set animation
      let rocketAnimation = Animation.named("my-json-rocket-animation")
      rocketAnimationView.animation = rocketAnimation
      rocketAnimationView.play()
}

When I build, the animation does not show--the view just remains blank. I have tried implementing the following in viewDidLoad(), which seems to work, but my animation does not scale to my entire view:

    let animation = Animation.named("my-json-rocket-animation")

    animationView.animation = animation
    animationView.contentMode = .scaleAspectFit
    view.addSubview(animationView)

    animationView.backgroundBehavior = .pauseAndRestore


    animationView.translatesAutoresizingMaskIntoConstraints = false
    animationView.topAnchor.constraint(equalTo: view.layoutMarginsGuide.topAnchor).isActive = true
    animationView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true

    animationView.bottomAnchor.constraint(equalTo: view.layoutMarginsGuide.bottomAnchor).isActive = true
    animationView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    animationView.setContentCompressionResistancePriority(.fittingSizeLevel, for: .horizontal)

I expected my animation to display in the view, but my screen remains blank. Do I need to create a new UIView and connect it with an IBOutlet, of class type AnimationView, and then somehow set the animation? I know this was possible by simply writing animationView.setAnimation(named: "my-json-rocket-animation") prior to version 3.1.2, but I'm not sure if it is still possible.

Answer 1

I'll post my solution for anyone who has trouble with this in the future, as I think Airbnb's documentation is a little vague regarding setting an animation to a UIView. The issue was that I essentially forgot to set the view's frame size, and I had to use an IBOutlet corresponding to the UIView.

import UIKit
import Lottie

class ViewController: UIViewController {


@IBOutlet weak var lottieView: UIView!
let animationView = AnimationView()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.

    animationView.animation = Animation.named("my-json-rocket-animation")
    animationView.frame.size = lottieView.frame.size
    animationView.contentMode = .scaleToFill

    lottieView.addSubview(animationView)
    animationView.backgroundBehavior = .pauseAndRestore

    animationView.play()

   }
}