Swift 将徽章添加到导航栏ButtonItem 和 UIButton

在Swift中，我们经常需要在导航栏ButtonItem和UIButton中添加徽章，以提醒用户有新的消息或者通知。本文将介绍如何使用自然语言来实现这个功能，并提供相应的案例代码。

swift
import UIKit
class BadgeView: UIView {
    private var label: UILabel
    
    override init(frame: CGRect) {
        label = UILabel(frame: frame)
        super.init(frame: frame)
        label.textColor = .white
        label.textAlignment = .center
        label.font = UIFont.systemFont(ofSize: 12)
        label.layer.cornerRadius = frame.size.height / 2
        label.layer.masksToBounds = true
        addSubview(label)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func setBadgeValue(value: Int) {
        label.text = "\(value)"
        if value == 0 {
            isHidden = true
        } else {
            isHidden = false
        }
    }
    
    // 设置徽章的颜色
    func setBadgeColor(color: UIColor) {
        label.backgroundColor = color
    }
}

swift
let badgeView = BadgeView(frame: CGRect(x: 0, y: 0, width: 20, height: 20))
badgeView.setBadgeValue(value: 3) // 设置徽章显示的数值
badgeView.setBadgeColor(color: .red) // 设置徽章的颜色
notificationButton.customView = badgeView

swift
import UIKit
extension UIButton {
    func addBadge(value: Int, color: UIColor, position: BadgePosition = .topRight, offset: CGPoint = .zero, size: CGFloat = 15) {
        let badgeView = BadgeView(frame: CGRect(x: 0, y: 0, width: size, height: size))
        badgeView.setBadgeValue(value: value)
        badgeView.setBadgeColor(color: color)
        
        let xPos: CGFloat
        let yPos: CGFloat
        
        switch position {
        case .topRight:
            xPos = frame.size.width - size + offset.x
            yPos = -offset.y
        case .topLeft:
            xPos = -offset.x
            yPos = -offset.y
        case .bottomRight:
            xPos = frame.size.width - size + offset.x
            yPos = frame.size.height - size + offset.y
        case .bottomLeft:
            xPos = -offset.x
            yPos = frame.size.height - size + offset.y
        }
        
        badgeView.frame.origin = CGPoint(x: xPos, y: yPos)
        addSubview(badgeView)
    }
}
enum BadgePosition {
    case topRight
    case topLeft
    case bottomRight
    case bottomLeft
}

swift
messageButton.addBadge(value: 2, color: .blue, position: .topRight, offset: CGPoint(x: 5, y: -5), size: 10)