iPhone旋转时CALayer的自动旋转

Question

我有一个UIViewController，在其中我将一个CALayer子类添加到视图的layer中：

[self.view.layer addSublayer:myObject.backgroundLayer];

当我旋转设备时，视图会旋转，但CALayer却没有旋转。它似乎被推到了左边，仍然保持竖屏视图。

有没有办法让子层自动旋转或者我需要应用一个变换？

- lfalin

Answer 1

使用Swift 4 / iOS 11，根据您的需求，您可以选择以下6个示例之一来管理设备旋转时的CALayer / CAGradientLayer框架。

以下示例使用CAGradientLayer，但可以轻松映射到CALayer或CAShapeLayer情况。

---

＃1.覆盖UIViewController viewDidLayoutSubviews()。

import UIKit

class ViewController: UIViewController {

    let gradientLayer: CAGradientLayer = {
        let layer = CAGradientLayer()
        layer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]
        return layer
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.layer.addSublayer(gradientLayer)
        gradientLayer.frame = view.bounds
    }

    override func viewDidLayoutSubviews() {         
        gradientLayer.frame = view.bounds
    }

}

#2. 覆盖UIViewController的loadView()方法，子类化UIView并覆盖UIView的layoutSubviews()方法

LayerView.swift

import UIKit

class LayerView: UIView {

    lazy var gradientLayer: CAGradientLayer = {
        let layer = CAGradientLayer()
        layer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]
        self.layer.addSublayer(layer)
        return layer
    }()

    override func layoutSubviews() {
        gradientLayer.frame = bounds
    }

}

LayerView.swift（替代方案）

import UIKit

class LayerView: UIView {

    var gradientLayer: CAGradientLayer!

    override func layoutSubviews() {
        if gradientLayer == nil {
            let gradientLayer = CAGradientLayer()
            gradientLayer.colors = [
                UIColor.blue.cgColor,
                UIColor.cyan.cgColor
            ]
            self.gradientLayer = gradientLayer
            layer.addSublayer(gradientLayer)
        }

        gradientLayer.frame = bounds
    }

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let layerView = LayerView()

    override func loadView() {
        view = layerView
    }

}

---

#3. Using Key Value Observing (KVO)

import UIKit

class ViewController: UIViewController {

    var observation: NSKeyValueObservation?

    let gradientLayer: CAGradientLayer = {
        let layer = CAGradientLayer()
        layer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]
        return layer
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        view.layer.addSublayer(gradientLayer)

        observation = view.observe(\.frame, options: [.new], changeHandler: { [unowned self] (object: UIView, change: NSKeyValueObservedChange<CGRect>) in
            guard let frame = change.newValue else { return }
            self.gradientLayer.frame = frame
        })

        // Also works
        /*
        observation = observe(\.view.frame, options: [.new], changeHandler: { [unowned self] (object: ViewController, change: NSKeyValueObservedChange<CGRect>) in
            guard let frame = change.newValue else { return }
            self.gradientLayer.frame = frame
        })
        */
    }

}

#4. 覆盖UIViewController的loadView()方法，子类化UIView并覆盖UIView的layerClass方法

LayerView.swift

import UIKit

class LayerView: UIView {

    override public class var layerClass: AnyClass {
        return CAGradientLayer.self
    }

    required init() {
        super.init(frame: .zero)

        guard let gradientLayer = layer as? CAGradientLayer else { return }
        gradientLayer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let layerView = LayerView()

    override func loadView() {
        view = layerView
    }

}

#5. 覆盖UIViewController的loadView()、子类化UIView并覆盖CALayerDelegate的layoutSublayers(of:)

LayerView.swift

import UIKit

class LayerView: UIView {

    required init() {
        super.init(frame: .zero)

        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]

        layer.addSublayer(gradientLayer)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutSublayers(of layer: CALayer) {
        layer.sublayers?.forEach {
            $0.frame = layer.bounds
        }
    }

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let layerView = LayerView()

    override func loadView() {
        view = layerView
    }

}

#6. 重写 UIViewController 的 loadView() 方法，继承 UIView 并重写 UIView 的 layerClass 方法，继承 CALayer 并重写 CALayer 的 layoutSublayers() 方法。

Layer.swift

import UIKit

class Layer: CALayer {

    override init() {
        super.init()

        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = [
            UIColor.blue.cgColor,
            UIColor.cyan.cgColor
        ]

        addSublayer(gradientLayer)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutSublayers() {
        sublayers?.forEach {
            $0.frame = bounds
        }
    }

}

LayerView.swift

import UIKit

class LayerView: UIView {

    override public class var layerClass: AnyClass {
        return Layer.self
    }

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let layerView = LayerView()

    override func loadView() {
        view = layerView
    }

}

---

Sources:

• medium.com
• github.com
• developer.apple.com

- Imanou Petit

---

你的代码有一些错误...如果你要重写一个函数，第一件事情是什么？...调用super。 - StackUnderflow

Answer 2

您需要自己管理CALayer的旋转。我相信0,0保持在原位，大小会根据新方向进行更改，因此如果您想要自己做一些事情，您需要自己管理旋转变换的添加。

- AlBlue