可以让屏幕上的元素立即旋转

Question

当我旋转我的设备时，屏幕中间的红色方块会移动以保持在屏幕中心，而不管旋转如何。但是，在旋转设备时，the square does not immediately reposition itself, instead the previous location of the square can be seen until the rotation animation is fully complete. 是否有一种方法可以让正方形在动画播放时立即重新定位，以便在旋转动画期间看不到它的旧位置？

import UIKit

class ViewController: UIViewController {
    var square = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()

        square.isHidden = true

        square = UIView(frame: CGRect(x: self.view.frame.width / 2 - 50, y: self.view.frame.height / 2 - 50, width: 100, height: 100))
        square.backgroundColor = UIColor.red
        self.view.addSubview(square)
        square.isHidden = false
    }

    override func didRotate(from fromInterfaceOrientation: UIInterfaceOrientation) {
        square.isHidden = true
        square = UIView(frame: CGRect(x: self.view.frame.width / 2 - 50, y: self.view.frame.height / 2 - 50, width: 100, height: 100))
        square.backgroundColor = UIColor.red
        self.view.addSubview(square)
        square.isHidden = false
    }
}

Answer 1

两件事：

1. didRotate 在 iOS 8 中已被弃用。它已被 viewWillTransition(to:with:) 取代。
2. 不要创建新方块。只需更新原始正方形的框架即可。

下面的代码创建一个正方形并设置autoresizingMask 使其保持居中。无需做任何其他事情。当然你也可以设置约束来代替autoresizingMask。

import UIKit

class ViewController: UIViewController {
    var square: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()

        square = UIView(frame: CGRect(x: self.view.frame.width / 2 - 50, y: self.view.frame.height / 2 - 50, width: 100, height: 100))
        square.backgroundColor = UIColor.red
        square.autoresizingMask = [ .flexibleLeftMargin, .flexibleRightMargin, .flexibleTopMargin, .flexibleBottonMargin ]
        self.view.addSubview(square)
    }
}