ios - UIView 自动旋转问题

Question

我在 UIView 的自动旋转中遇到问题，它只是一条红线，宽度为 4，高度是横向模式下 superview 高度的一半，而在纵向模式下，高度是 4 点，宽度是 superview 宽度的一半。你可以在 gif 中看到这个问题。当我从横向旋转到纵向时，自动旋转的效果不平滑并且有扭曲。

这是代码。我做错了什么？

private var myView:UIView!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    myView = UIView(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width/2, height: 4))
    myView.backgroundColor = UIColor.red
    view.addSubview(myView)

    myView.center = CGPoint(x: view.bounds.width/2, y: view.bounds.height/2)


}

private func layoutMyView() {

    let orientation = UIApplication.shared.statusBarOrientation

    if orientation == .landscapeLeft || orientation == .landscapeRight {
        myView.frame = CGRect(x: 0, y: 0, width: view.bounds.width/2, height: 4)
    } else {
        myView.frame = CGRect(x: 0, y: 0, width: 4, height: view.bounds.height/2)
    }

    myView.center = CGPoint(x: view.bounds.width/2, y: view.bounds.height/2)
}


override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

    let orientation = UIApplication.shared.statusBarOrientation

    NSLog("View will transition to \(size), \(orientation.rawValue)")

    if size.width < size.height {
        NSLog("Portrait mode")
    } else {
        NSLog("Landscape mode")
    }

    super.viewWillTransition(to: size, with: coordinator)

    coordinator.animate(alongsideTransition: { [unowned self] (_) in

        let orient = UIApplication.shared.statusBarOrientation

         self.layoutMyView()

        }, completion: { [unowned self] (UIViewControllerTransitionCoordinatorContext) -> Void in

            let orient = UIApplication.shared.statusBarOrientation
            self.layoutMyView()
            NSLog("rotation completed to \(orient.rawValue), \(self.myView.frame)")
    })
}

Answer 1

有几个可能的选择:

1. 在 animate(alongsideTransition:completion:) 中，做一个关键帧动画来设置中间动画点，这样你就不会以那种奇怪的方形感觉结束动画。例如。这将它缩小到一个 4x4 的盒子

   override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
       super.viewWillTransition(to: size, with: coordinator)
   
       let origin = CGPoint(x: (view.bounds.midX + view.bounds.midY) / 2 - 2,
                            y: (view.bounds.midX + view.bounds.midY) / 2 - 2)
   
       coordinator.animate(alongsideTransition: { _ in
           UIView.animateKeyframes(withDuration: coordinator.transitionDuration, delay: 0, animations: {
               UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5) {
                   self.myView.frame = CGRect(origin: origin, size: CGSize(width: 4, height: 4))
               }
   
               UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5) {
                   self.layoutMyView()
               }
           })
       })
   }
   

   这个主题有很多可能的变体。这仍然使 View 充满活力，但赋予它一种更“深思熟虑”的氛围，并且不会失去它的“线条”感觉。

   

2. 与其使用 UIView 渲染“线”，不如使用 CAShapeLayer并更新其 path .

3. 你可以运行 CADisplayLink当过渡正在进行时，然后随着动画的进行将帧更新为您想要的任何内容。

4. 您可以为该 View 的 transform 设置动画，而不是为 frame 设置动画，可以将其旋转到与 View 旋转相反的方向。