iPhone 旋转时 CALayer 自动旋转

Question

我有一个 UIViewController，其中我将 CALayer 子类添加到视图层：

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

当我旋转设备时，视图会旋转，但 CALayer 不会旋转。它有点被分流到左边，仍然是纵向视图。

有没有办法让子图层自动旋转或者我需要应用变换？

Answer 1

使用 Swift 4 / iOS 11，根据您的需要，您可以选择以下6 个示例之一，以便在设备旋转时管理您的CALayer/框架。CAGradientLayer

下面的示例使用CAGradientLayer但可以轻松映射到CALayer或CAShapeLayer案例。

#1. 压倒一切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. 重写UIViewController loadView()、子类化UIView和重写UIView layoutSubviews()

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）

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。使用键值观察 (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。重写UIViewController loadView()、子类化UIView和重写UIView layerClass

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。重写UIViewController loadView()、子类化UIView和重写CALayerDelegate 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 loadView()、子类化UIView、重写UIView layerClass、子类化CALayer和重写CALayer layoutSublayers()

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
    }

}

资料来源：

• 媒体网站
• github.com
• 开发者.apple.com