如何在UISegmentedControl中仅显示所选项目的底部边框？

我是iOS开发的新手，在为课程构建应用程序时遇到了一些麻烦。

我创建了一个分段控件，它的init函数（如下所示）在包含分段控件的视图控制器类中调用。 我能够从分段控件类中删除分段控件的所有边框和分隔符，如下所示：

import Foundation import UIKit class CashSegmentedControl: UISegmentedControl{ func initUI(){ removeBorders() } func removeBorders(){ self.tintColor = UIColor.clear } 

我希望它在每个段下面都有一条线当选择了段时（类似于instagram）

我搜索了很多，并在StackOverflow上发现了一些post，但它们似乎是旧版本的Swift。 我真的很感激这方面的任何帮助，如果有更好的解决方案来定制边界（除了我所做的），我想要了解更多！

非常感谢 ：）

Answer 1

在单独的swift文件中添加以下代码（命令+ N – >新文件）：

 extension UISegmentedControl{ func removeBorder(){ let backgroundImage = UIImage.getColoredRectImageWith(color: UIColor.white.cgColor, andSize: self.bounds.size) self.setBackgroundImage(backgroundImage, for: .normal, barMetrics: .default) self.setBackgroundImage(backgroundImage, for: .selected, barMetrics: .default) self.setBackgroundImage(backgroundImage, for: .highlighted, barMetrics: .default) let deviderImage = UIImage.getColoredRectImageWith(color: UIColor.white.cgColor, andSize: CGSize(width: 1.0, height: self.bounds.size.height)) self.setDividerImage(deviderImage, forLeftSegmentState: .selected, rightSegmentState: .normal, barMetrics: .default) self.setTitleTextAttributes([NSForegroundColorAttributeName: UIColor.gray], for: .normal) self.setTitleTextAttributes([NSForegroundColorAttributeName: UIColor(red: 67/255, green: 129/255, blue: 244/255, alpha: 1.0)], for: .selected) } func addUnderlineForSelectedSegment(){ removeBorder() let underlineWidth: CGFloat = self.bounds.size.width / CGFloat(self.numberOfSegments) let underlineHeight: CGFloat = 2.0 let underlineXPosition = CGFloat(selectedSegmentIndex * Int(underlineWidth)) let underLineYPosition = self.bounds.size.height - 1.0 let underlineFrame = CGRect(x: underlineXPosition, y: underLineYPosition, width: underlineWidth, height: underlineHeight) let underline = UIView(frame: underlineFrame) underline.backgroundColor = UIColor(red: 67/255, green: 129/255, blue: 244/255, alpha: 1.0) underline.tag = 1 self.addSubview(underline) } func changeUnderlinePosition(){ guard let underline = self.viewWithTag(1) else {return} let underlineFinalXPosition = (self.bounds.width / CGFloat(self.numberOfSegments)) * CGFloat(selectedSegmentIndex) UIView.animate(withDuration: 0.1, animations: { underline.frame.origin.x = underlineFinalXPosition }) } } extension UIImage{ class func getColoredRectImageWith(color: CGColor, andSize size: CGSize) -> UIImage{ UIGraphicsBeginImageContextWithOptions(size, false, 0.0) let graphicsContext = UIGraphicsGetCurrentContext() graphicsContext?.setFillColor(color) let rectangle = CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height) graphicsContext?.fill(rectangle) let rectangleImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return rectangleImage! } } 

然后从viewDidLoad()方法调用segmentedControl.addUnderlineForSelectedSegment()之后，为分段控件创建一个@IBAction方法，如下所示：

 @IBAction func segmentedControlDidChange(_ sender: UISegmentedControl){ segmentedControl.changeUnderlinePosition() } 

然后从此方法中调用segmentedControl.changeUnderlinePosition() 。

不要忘记将故事板中的分段控件连接到刚刚创建的@IBAction方法。

非常重要 ：不要忘记在故事板中使用自动布局来确定分段控件的大小和位置。

这是结果：

随意问你可能有的任何其他问题:)

Answer 2

A.Jam在Xcode 9.3，Swift 4.2版本中的答案

 import UIKit extension UISegmentedControl { func removeBorder(){ let backgroundImage = UIImage.getColoredRectImageWith(color: UIColor.white.cgColor, andSize: self.bounds.size) self.setBackgroundImage(backgroundImage, for: .normal, barMetrics: .default) self.setBackgroundImage(backgroundImage, for: .selected, barMetrics: .default) self.setBackgroundImage(backgroundImage, for: .highlighted, barMetrics: .default) let deviderImage = UIImage.getColoredRectImageWith(color: UIColor.white.cgColor, andSize: CGSize(width: 1.0, height: self.bounds.size.height)) self.setDividerImage(deviderImage, forLeftSegmentState: .selected, rightSegmentState: .normal, barMetrics: .default) self.setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.gray], for: .normal) self.setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor(red: 67/255, green: 129/255, blue: 244/255, alpha: 1.0)], for: .selected) } func addUnderlineForSelectedSegment(){ removeBorder() let underlineWidth: CGFloat = self.bounds.size.width / CGFloat(self.numberOfSegments) let underlineHeight: CGFloat = 2.0 let underlineXPosition = CGFloat(selectedSegmentIndex * Int(underlineWidth)) let underLineYPosition = self.bounds.size.height - 1.0 let underlineFrame = CGRect(x: underlineXPosition, y: underLineYPosition, width: underlineWidth, height: underlineHeight) let underline = UIView(frame: underlineFrame) underline.backgroundColor = UIColor(red: 67/255, green: 129/255, blue: 244/255, alpha: 1.0) underline.tag = 1 self.addSubview(underline) } func changeUnderlinePosition(){ guard let underline = self.viewWithTag(1) else {return} let underlineFinalXPosition = (self.bounds.width / CGFloat(self.numberOfSegments)) * CGFloat(selectedSegmentIndex) UIView.animate(withDuration: 0.1, animations: { underline.frame.origin.x = underlineFinalXPosition }) } } extension UIImage { class func getColoredRectImageWith(color: CGColor, andSize size: CGSize) -> UIImage{ UIGraphicsBeginImageContextWithOptions(size, false, 0.0) let graphicsContext = UIGraphicsGetCurrentContext() graphicsContext?.setFillColor(color) let rectangle = CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height) graphicsContext?.fill(rectangle) let rectangleImage = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return rectangleImage! } } 

Answer 3

你可以用它

 let segmentBottomBorder = CALayer() segmentBottomBorder?.borderColor = UIColor.blue.cgColor segmentBottomBorder?.borderWidth = 3 let x = CGFloat(sender.selectedSegmentIndex) * width let y = sender.frame.size.height - (segmentBottomBorder?.borderWidth)! let width: CGFloat = sender.frame.size.width/3 segmentBottomBorder?.frame = CGRect(x: x, y: y, width: width, height: (segmentBottomBorder?.borderWidth)!) sender.layer.addSublayer(segmentBottomBorder!)