快速将NavigationBar底部边框更改为虚线

时间:2019-02-22 00:43:38

标签: ios swift xcode

我想将我的navigationBar更改为以虚线为边框,如下所示:

screenshot

我在此主题中找到了一个很好的答案,有关如何更改NavigationBar边框的颜色:Change navigation bar bottom border color Swift特别是:https://stackoverflow.com/a/46224261/436014

通过UIColor扩展名:

extension UIColor {

    /// Converts this `UIColor` instance to a 1x1 `UIImage` instance and returns it.
    ///
    /// - Returns: `self` as a 1x1 `UIImage`.
    func as1ptImage() -> UIImage {
        UIGraphicsBeginImageContext(CGSize(width: 1, height: 1))
        setFill()
        UIGraphicsGetCurrentContext()?.fill(CGRect(x: 0, y: 0, width: 1, height: 1))
        let image = UIGraphicsGetImageFromCurrentImageContext() ?? UIImage()
        UIGraphicsEndImageContext()
        return image
    }
}

我想知道是否有任何方法可以改编虚线。我本以为可以通过以多种颜色填充填充来完成此操作,但由于它是单个UIcolor的扩展,因此感到困惑

navigationController.navigationBar.shadowImage = UIColor.black.as1ptImage()

因此,类似以下内容显然不起作用:

UIGraphicsBeginImageContext(CGSize(width: 1, height: 4))
UIGraphicsGetCurrentContext()?.fill(CGRect(x: 0, y: 0, width: 1, height: 1))
UIGraphicsGetCurrentContext()?.fill(CGRect(x: 1, y: 0, width: 3, height: 1))

我想知道是否有人知道如何解决这个问题

1 个答案:

答案 0 :(得分:0)

好的,我设法借助CALayer的API文档找到了解决方案:https://developer.apple.com/documentation/quartzcore/cashapelayer/1521921-linedashpattern

这个关于将CALayer转换为UIImage的线程:UIImage from CALayer in iOS

整个过程是:

  1. 创建一个CALayer
  2. 为此CALayer赋予一个框架
  3. 画一条虚线
  4. 转换为UIImage
  5. 将此UIImage用作navigationBar.shadowImage

有趣的是,它可以适当地平铺,因此CALayer / UIImage只需与您生成的虚线一样宽。

    extension UIImage {
        class func imageWithLayer(layer: CALayer) -> UIImage {
            UIGraphicsBeginImageContextWithOptions(layer.bounds.size, layer.isOpaque, 0.0)
            layer.render(in: UIGraphicsGetCurrentContext()!)
            guard let img = UIGraphicsGetImageFromCurrentImageContext() else { return UIImage() }
            UIGraphicsEndImageContext()
            return img
        }
    }


    let layer = CALayer()
    layer.frame = CGRect(x: 0, y: 0, width: 6, height: 1)
    let shapeLayer = CAShapeLayer()
    shapeLayer.strokeColor = UIColor.black.cgColor
    shapeLayer.lineWidth = 1
    shapeLayer.lineDashPattern = [4,2]
    let path = CGMutablePath()
    path.addLines(between: [CGPoint(x:1, y: 0), CGPoint(x: 6, y:0)])
    shapeLayer.path = path
    layer.addSublayer(shapeLayer)
    navigationController.navigationBar.shadowImage = UIImage.imageWithLayer(layer: layer)