SOLVED: Multiple scheduled UI updates don't work

@MarinaBSA

Dec '20

I am trying to make an image "move down" every second while also showing a time counter. I have a scheduledTimer where I change the image's Y center and update the timer. The timer label updates but the image does not move. Strangely I can get the image to move down if I comment the line where I update the timer's UILabel. So appearently I can't update both.

class ViewController: UIViewController {

    let starImage = UIImageView(image: UIImage(systemName: "star.fill"))
    let timerLabel = UILabel()
    var counter = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .black

        setupViews()
        gameEngine()
    }

    private func setupViews() {
        // SETTING LAYOUT CONSTRAINTS HERE -- not relevant for this issue
        ...
    }

    // PROBLEM HERE
    private func gameEngine() {
        Timer.scheduledTimer(withTimeInterval: 1, repeats: true) {
            [weak self] _ in
            self?.counter += 1
            self?.timerLabel.text = "Timer: \(self!.counter)"
            self?.starImage.center.y += 1
        }
    }

}

I tried adding the timer to the RunLoop, but I get the same results. I also tried doing it on a separated DispatchQueue. Any help will truly appreciated.

@MarinaBSA

Dec '20

Answering my own question all I had to do was to keep a reference to the topConstraint of the image so I could update it everytime it was supposed to move down.

   // Declare constraint
    var starImageTopConstraint: NSLayoutConstraint!

    // Later when setting constraints
    starImageTopConstraint = starImage.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: -30)

     NSLayoutConstraint.activate([
        ...
        starImageTopConstraint,
        ...
      ])

    // When I wish to move the image down by X
    starImageTopConstraint.constant += X

Sponsor Hacking with Swift and reach the world's largest Swift community!

Archived topic

This topic has been closed due to inactivity, so you can't reply. Please create a new topic if you need to.

All interactions here are governed by our code of conduct.