Animating UIIMageView Alpha on view did load - ios

Question

I am attempting to animate the background image of my HomeController.
I would like to fade the image in, as such I was hoping to animate it's alpha property.
I have found many answers on here around this, however many seem dated (obj c, iOS 3/4/5 etc) and following the recommended approach, I still cannot get this animation to work.
Can anyone please tell me what is wrong with my code?
I would like to animate backgroundImage. I have placed my animation code at the end of my setupView method.
It does not 'fade in' as I would like, essentially the alpha jumps straight to 0.7
import UIKit
class HomeController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
setupView()
}
private let backgroundImage: UIImageView = {
let image = UIImageView()
image.image = #imageLiteral(resourceName: "foggy").withRenderingMode(.alwaysOriginal)
image.contentMode = .scaleToFill
image.alpha = 0
image.isOpaque = false
return image
}()
private let currentLocation: UIButton = {
let button = UIButton(type: .system)
button.setTitle("Southampton, UK", for: .normal)
button.titleLabel?.font = UIFont.systemFont(ofSize: 24)
button.contentMode = .center
button.setTitleColor(.black, for: .normal)
button.addTarget(self, action: #selector(onPressLocation), for: .touchUpInside)
return button
}()
private let currentTemp: UIButton = {
let button = UIButton(type: .system)
button.setTitle("37°C", for: .normal)
button.titleLabel?.font = UIFont.systemFont(ofSize: 54, weight: .thin)
button.contentMode = .center
button.setTitleColor(.white, for: .normal)
button.addTarget(self, action: #selector(onPressTemp), for: .touchUpInside)
return button
}()
}
extension HomeController {
#objc fileprivate func onPressLocation() -> Void {
print("Location pressed.")
}
#objc fileprivate func onPressTemp() -> Void {
self.currentTemp.setTitle("98°F", for: .normal)
}
fileprivate func setupView() -> Void {
view.backgroundColor = .white
// MARK: Background Image
view.addSubview(backgroundImage)
backgroundImage.anchor(
top: view.safeAreaLayoutGuide.topAnchor,
left: view.safeAreaLayoutGuide.leftAnchor,
bottom: view.safeAreaLayoutGuide.bottomAnchor,
right: view.safeAreaLayoutGuide.rightAnchor,
paddingTop: 0,
paddingLeft: 0,
paddingBottom: 0,
paddingRight: 0,
width: 0,
height: 0
)
// MARK: Current Location
view.addSubview(currentLocation)
currentLocation.anchor(
top: view.safeAreaLayoutGuide.topAnchor,
left: view.safeAreaLayoutGuide.leftAnchor,
right: view.safeAreaLayoutGuide.rightAnchor,
paddingTop: 50,
paddingLeft: 0,
paddingBottom: 0,
paddingRight: 0,
width: 0,
height: 26,
centerX: view.centerXAnchor
)
// MARK: Temp Button
view.addSubview(currentTemp)
currentTemp.anchor(
top: currentLocation.bottomAnchor,
paddingTop: 10,
paddingLeft: 0,
paddingBottom: 0,
paddingRight: 0,
width: 200,
height: 70,
centerX: view.centerXAnchor
)
// MARK: Animations
UIView.animate(withDuration: 6, delay: 3, options: .curveEaseInOut, animations: {
self.backgroundImage.alpha = 0.7
}, completion: nil)
}
}

Answer 1

IBOutlets does not get visible when viewDidLoad is called so call your setupView method in viewDidAppear which is called after your view appeared on screen.
Hope this helps.

Answer 2

You can put your code in viewDidAppear view life cycle method for any animation work ,because viewDidAppear method notifies the view controller that its view was added to a view hierarchy.Use below code for your solution.
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated: animated)
//Call method like this
setupView()
}