swift中的渐变效果

项目为了更好的视觉呈现，可能会使用到渐变效果。若是一两处的话，可以让UI切下图，但很多时候还是得靠自己代码去弄

• 使用CAGradientLayer：

1.colors(CGColor）设置显示的颜色,

2.startPoint/endPoint（0.0~1.1）设置颜色起始/终点位置，左上角（0.0），右下角（1.1）

class myBtn:UIButton {
    /// 渐变层
    lazy var bgLayer: CAGradientLayer = {
        let lay = CAGradientLayer()
        lay.colors = [UIColor.black.cgColor, UIColor.green.cgColor]//设置颜色
        lay.startPoint = CGPoint(x: 0.5, y: 1)//起始位置
        lay.endPoint = CGPoint(x: 1, y: 0)//结束位置
        return lay
    }()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.layer.insertSublayer(bgLayer, at: 0)//将渐变层添加到控件上
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        //渐变层需要确定大小
        self.bgLayer.frame = CGRect(x: 0, y: 0, width: self.frame.width, height: self.frame.height)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

主要内容就是上面这点 

• 为了方便项目中的使用，我这里做了一个简单的封装，兼容深色模式的处理

需要主动监听手机模式的变化

• extension Notification.Name {
      ///手机深色模式切换的通知
      static let TraitCollectionDidChangeNotification =  NSNotification.Name("TraitCollectionDidChangeNotification")
  }

   

对UIViewController使用交换方法（之前我写过一片文章中用过HZJSwizzlingProtocol）

// MARK: - 交换方法
extension UIViewController:HZJSwizzlingProtocol {
    
    static func Swizzling() {
        self.changeMethod(#selector(traitCollectionDidChange(_:)), selector2: #selector(hzj_traitCollectionDidChange(_:)))
    }
    
    /// 交换
    static func changeMethod(_ selector1:Selector, selector2:Selector) {
        guard let method1 = class_getInstanceMethod(self, selector1) else {return}
        guard let method2 = class_getInstanceMethod(self, selector2) else {return}
        if (class_addMethod(self, selector1, method_getImplementation(method2), method_getTypeEncoding(method2))) {
            class_replaceMethod(self, selector2, method_getImplementation(method1), method_getTypeEncoding(method1))
        } else {
            method_exchangeImplementations(method1, method2)
        }
    }
    
    /// 深色模式切换时，发送通知
    /// - Parameter previousTraitCollection: <#previousTraitCollection description#>
    @objc func hzj_traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        self.hzj_traitCollectionDidChange(previousTraitCollection)
        NotificationCenter.default.post(name: .TraitCollectionDidChangeNotification, object: previousTraitCollection)
    }
}

然后就是封装了

class HZJGradientLayer: CAGradientLayer {
    
    private var _allColors:[UIColor] = []
    
    /// 便于直接通过UIColor设置渐变色
    var allColors:[UIColor]{
        set{
            self._allColors = newValue
            self.colors = newValue.map{$0.cgColor}
        }
        get{
            return _allColors
        }
    }
    ///当前的手机模式
    private var layerType:UITraitCollection?{
        didSet{
            if self.layerType != oldValue {
                self.colors = self.allColors.map{$0.cgColor}
            }
        }
    }
    ///构造方法
    init(_ colors:[UIColor] = [UIColor.black.withAlphaComponent(0.05),UIColor.green.withAlphaComponent(0.25)], start:CGPoint = CGPoint(x: 0.5, y: 0), end:CGPoint = CGPoint(x: 1, y: 1)) {
        super.init()
        if #available(iOS 13.0, *) {
            self.layerType = .current
        } else {
            
        }
        self.allColors = colors
        self.startPoint = start
        self.endPoint = end
        //接收模式改变的通知
        NotificationCenter.default.addObserver(self, selector: #selector(changeModel(_:)), name: .TraitCollectionDidChangeNotification, object: nil)
    }
    
    private override init() { super.init() }
    
    private override init(layer: Any) { super.init(layer: layer) }
    
    deinit {
        NotificationCenter.default.removeObserver(self, name: .TraitCollectionDidChangeNotification, object: nil)
    }
    
    @objc func changeModel(_ noti:Notification) {
        if let type = noti.object as? UITraitCollection{
            self.layerType = type
        }
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

用法和之前一样，只是颜色可以用过allColors直接用uicolor设置,而且支持深色模式了

来源：oschina

链接：https://my.oschina.net/wshzj/blog/4314163