我正在尝试通过改变transform来实现UITextView的动画效果。但在动画过程中会使文本消失。以下是我的测试代码。
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()
}
}
}
我尝试使用故事板,但结果相同。当我使用UIView.animate
方法时,结果也是一样的。为什么会这样?我想在文本上启用动画。
更新
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()
}
我用这段代码进行了测试,得到了相同的结果。