UITextView text disappears after applying transform - ios

Question

I have a simple UITextView with a custom NSLayoutManager in my app. The UITextView have a tap gesture and when you tap on UITextView it animates off the screen. My problem is that when you tap on the UITextView the entire text disappears. After debugging for a while I think it has something to do with NSTextContainer which I pass to the UITextView because If I don't pass it everything works fine. I thought it had to do something with my custom NSLayoutManager but then I tested it with a default NSLayoutManger and it is still giving the same issue.
Can you please tell me what is going wrong? I have attached a sample code for your reference. I have slowed down the animation so can see what is wrong.
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
setUpTextView()
}
private func setUpTextView() {
let rect = CGRect(origin: CGPoint(x: view.frame.origin.x,
y: view.frame.origin.y + 50
),
size: CGSize(width: view.frame.width,
height: view.frame.height - 50
)
)
let textView = MyTextView(frame: rect)
textView.backgroundColor = .gray
textView.layer.cornerRadius = 15
textView.textContainerInset.left = view.frame.width * 0.05
textView.textContainerInset.right = view.frame.width * 0.05
textView.textContainerInset.top = view.frame.height * 0.05
textView.textContainerInset.bottom = view.frame.height * 0.05
let string = "The Ultimate Fighting Championship is an American mixed martial arts promotion company based in Las Vegas, Nevada."
let attributedText = NSAttributedString(string: string, attributes: [
.font: UIFont.systemFont(ofSize: 24, weight: .semibold),
.foregroundColor: UIColor.white
])
textView.attributedText = attributedText
textView.isScrollEnabled = false
textView.isEditable = false
textView.isSelectable = false
view.addSubview(textView)
}
}
MyTextView
class MyTextView: UITextView {
override init(frame: CGRect, textContainer: NSTextContainer?) {
let textStorage = NSTextStorage()
let layoutManager = NSLayoutManager()
textStorage.addLayoutManager(layoutManager)
let textContainer = NSTextContainer(size: frame.size)
layoutManager.addTextContainer(textContainer)
super.init(frame: frame, textContainer: textContainer)
addGesture()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private func addGesture() {
let gesture = UITapGestureRecognizer(target: self, action: #selector(handleTap))
addGestureRecognizer(gesture)
}
#objc func handleTap(gesture: UITapGestureRecognizer) {
UIView.animate(withDuration: 10, delay: 0) {
self.transform = CGAffineTransform(translationX: 0, y: self.frame.height)
}
}
}

Answer 1

The problem you're running into is that you are positioning your view "off-screen."
When UIKit generates the animation, it calculates the final position and decides that, because your text view will no longer be visible, it doesn't need to render the text container content.
If you want to continue using transform (although, I'd advise against that and instead use auto-layout), you can fix your disappearing text by animating the textView so 1-point is still inside the view's bounds, and then moving it the final point in the completion block.
Something like this:
UIView.animate(withDuration: 10.0, animations: {
self.transform = CGAffineTransform(translationX: 0, y: self.frame.height - 1.0)
}, completion: { _ in
self.transform = CGAffineTransform(translationX: 0, y: self.frame.height)
})