CODEWITHSUNDEEP
iosswiftanimationuitextview
Paul
Paul

Reputation: 789

Animating UITextView cause text disappeared while animation

I am trying to animate UITextView by changing transform. But it makes text disappered while animating. Here is my test code.

class ViewController: UIViewController {
    let textView = UITextView()

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        textView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(textView)
        
        textView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        textView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        textView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
        textView.heightAnchor.constraint(equalToConstant: 300).isActive = true
        textView.backgroundColor = .systemOrange
        textView.text = "abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd"
        textView.textColor = .white

        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            let animator = UIViewPropertyAnimator(duration: 2, curve: .easeInOut, animations:  {
                self.textView.transform = CGAffineTransform(translationX: 0, y: 1000)
            })
            animator.startAnimation()
        }
    }
}

Demo

I tried with storyboard but the result was same. Same result when I use UIView.animate method.

Why does this happen? I want to animate it with text on.

UPDATE

let contraint = textView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor)
contraint.isActive = true

DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
    contraint.constant = 1000
    let animator = UIViewPropertyAnimator(duration: 2, curve: .easeInOut, animations:  {
        self.view.layoutIfNeeded()
    })
    animator.startAnimation()
}

I tested with this code, and got same result.

Upvotes: 5

Views: 622

Answers (1)

matt
matt

Reputation: 536009

I'm afraid you'll have to animate a snapshot view instead:

DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
    let v = self.textView.snapshotView(afterScreenUpdates: true)!
    v.frame = self.textView.frame
    self.view.addSubview(v)
    self.textView.isHidden = true
    let animator = UIViewPropertyAnimator(duration: 2, curve: .easeInOut, animations:  {
        v.frame.origin.y = 1000
    })
    animator.startAnimation()
}

I don't think that's a bad solution; this is what snapshot views are for, after all.

Upvotes: 4

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