Cannot animate UIImage with timing delay in Swift

Question

I am attempting to animate the alpha of a UIImage after 3 seconds has passed. By default the alpha is set to 0 and after 3 seconds, the alpha should change to 1, thus displaying the image to the user. My code I wrote for my animation does set the alpha to 0, but I am unable to change the the alpha to 1 after 3 seconds. I am newer to swift and not sure where I am going wrong with this. Here is my code.

import UIKit

class WelcomeOneViewController: UIViewController {

@IBOutlet weak var swipeImageView: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()
    swipeImageView.alpha = 0
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    displaySwipeView()
}

func displaySwipeView() {
    UIView.animate(withDuration: 1.0, delay: 3.0, options: .beginFromCurrentState, animations: {

        DispatchQueue.main.async { [weak self] in
            self?.swipeImageView.alpha = 1
        }

    }, completion: nil)
}

}

If you want your animation should complete in 3 second then withDuration: 1.0, should be withDuration: 3.0, — Prashant Tukadiya
– Prashant Tukadiya, Commented Feb 13, 2018 at 13:45
I want the animation to begin after a 3 second delay, not take 3 seconds to complete. — Andrew Tuzson
– Andrew Tuzson, Commented Feb 13, 2018 at 13:45
From where are you calling this method ? Make sure it is view will appear not view did load and also try in main queue — Prashant Tukadiya
– Prashant Tukadiya, Commented Feb 13, 2018 at 13:46

Milan Nosáľ · Accepted Answer · 2018-02-13 14:23:57Z

2

Try it with this code:

import UIKit

class WelcomeOneViewController: UIViewController {

    @IBOutlet weak var swipeImageView: UIImageView!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        swipeImageView.alpha = 0
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        displaySwipeView()
    }

    func displaySwipeView() {
        swipeImageView.alpha = 0
        UIView.animate(withDuration: 1.0, delay: 3.0, options: [], animations: {
            self.swipeImageView.alpha = 1
        }, completion: nil)
    }

}

edited Feb 13, 2018 at 14:23

answered Feb 13, 2018 at 14:03

Milan Nosáľ

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6 Comments

Andrew Tuzson Over a year ago

That didn't do the trick. The image is still visible immediately when the view loads.

Milan Nosáľ Over a year ago

@AndrewTuzsonhow about now?

Andrew Tuzson Over a year ago

That did the trick! However, now the image is visible for a split second before it disappears. How do I overcome that?

Andrew Tuzson Over a year ago

Would I use swipeImageView.alpha = 0 in viewWillAppear?

Milan Nosáľ Over a year ago

@AndrewTuzson that means that somewhere between viewDidLoad and viewDidAppear you are setting swipeImageView.alpha to 1 again.. try putting swipeImageView.alpha = 0 to viewWillAppear()

|

Agent Smith · Accepted Answer · 2018-02-13 13:45:53Z

1

Try doing it on main queue like this:

func displaySwipeView() {
  UIView.animate(withDuration: 1.0, delay: 3.0, options: .beginFromCurrentState, animations: {

   DispatchQueue.main.async { [weak self] in
    self?.swipeImageView.alpha = 1
   }

  }, completion: nil)
}

Hope it helps!!

answered Feb 13, 2018 at 13:45

Agent Smith

3,03321 silver badges37 bronze badges

6 Comments

Andrew Tuzson Over a year ago

Thanks! I copied over your syntax and called displaySwipeView() in viewDidLoad() after setting the alpha to 0. The image is now visible when the screen loads. Any ideas?

Agent Smith Over a year ago

So the problem now is, if I'm right, that image loads but without animation?

Andrew Tuzson Over a year ago

That is correct. The image is displayed immediately when the view is loaded. I have updated the syntax in the original post.

Milan Nosáľ Over a year ago

putting it on the main thread is useless.. viewDidLoad is executed on the main thread already

Agent Smith Over a year ago

@AndrewTuzson Try using any other UIViewAnimationOptions. Other than .beginFromCurrentState try using .curveEaseInOut. beginFromCurrentState sometimes shows unexpected behaviour.

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