Swift：仿QQ导航栏渐变色背景

实现的效果图：

网上所谓的渐变大多数的都是界面滑动时导航栏透明度的改变，特此开一篇文章出来做记录，共同学习

其实渐变色很简单，利用CAGradientLayer即可。直接上代码：

letgradientLayer =CAGradientLayer()

let sizeLength = self.navigationController?.navigationBar.frame.width

letframeAndStatusBar =CGRect(x:0, y:0, width: sizeLength!, height:64)

gradientLayer.frame= frameAndStatusBar

gradientLayer.startPoint=CGPoint(x:0, y:0)

gradientLayer.endPoint=CGPoint(x:1, y:0)

gradientLayer.colors = [UIColor.blue.cgColor, UIColor.red.cgColor]

navigationController?.navigationBar.setBackgroundImage(LayerImage(fromLayer: gradientLayer), for: .default)

LayerImage函数如下：

func LayerImage(fromLayer layer:CALayer) ->UIImage{

        UIGraphicsBeginImageContext(layer.frame.size)

        layer.render(in: UIGraphicsGetCurrentContext()!)

        let outputImage = UIGraphicsGetImageFromCurrentImageContext()

        UIGraphicsEndImageContext()

        returnoutputImage!

    }