优化UIButton：实现更清晰的按压视觉反馈效果

1. 利用UIButton内置配置（iOS 15+） #

iOS 15及以上版本的UIButton新增了configuration属性，可直接配置与系统按钮一致的按压反馈：

let customButton = UIButton(type: .system)
// 初始化基础纯样式配置
var config = UIButton.Configuration.plain()
config.title = "自定义按钮"
// 设置常态与按压态背景
config.background.backgroundColor = .systemGray6
config.background.cornerRadius = 8
config.background.highlightedColor = .systemGray4
// 应用配置
customButton.configuration = config

这种方式无需额外逻辑，就能让按钮拥有和照片选择器按钮一致的按压视觉反馈。

2. 自定义高亮状态样式（兼容iOS 15以下） #

针对低版本系统，可通过重写isHighlighted属性，手动切换按钮样式：

class HighlightableButton: UIButton {
    override var isHighlighted: Bool {
        didSet {
            // 切换背景色
            backgroundColor = isHighlighted ? .systemGray4 : .systemGray6
            // 可选：添加缩放动画强化反馈
            UIView.animate(withDuration: 0.1) {
                self.transform = self.isHighlighted ? CGAffineTransform(scaleX: 0.95, y: 0.95) : .identity
            }
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupBaseStyle()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupBaseStyle()
    }
    
    private func setupBaseStyle() {
        backgroundColor = .systemGray6
        layer.cornerRadius = 8
        setTitle("自定义按钮", for: .normal)
        setTitleColor(.systemBlue, for: .normal)
    }
}

这种方式完全自定义，可根据需求调整高亮时的颜色、缩放比例等细节。

3. 添加按压波纹效果（模拟系统触感） #

如果想要类似系统的波纹扩散反馈，可通过触摸事件实现：

class RippleButton: UIButton {
    private var rippleLayer: CAShapeLayer?
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        guard let touch = touches.first else { return }
        let touchPoint = touch.location(in: self)
        
        // 创建波纹图层
        rippleLayer = CAShapeLayer()
        rippleLayer?.fillColor = UIColor.systemGray3.withAlphaComponent(0.5).cgColor
        rippleLayer?.path = UIBezierPath(ovalIn: CGRect(x: touchPoint.x - 5, y: touchPoint.y - 5, width: 10, height: 10)).cgPath
        layer.addSublayer(rippleLayer!)
        
        // 波纹扩散动画
        let scaleAnim = CABasicAnimation(keyPath: "transform.scale")
        scaleAnim.fromValue = 1
        scaleAnim.toValue = max(bounds.width, bounds.height) / 10
        
        let alphaAnim = CABasicAnimation(keyPath: "opacity")
        alphaAnim.fromValue = 0.5
        alphaAnim.toValue = 0
        
        let groupAnim = CAAnimationGroup()
        groupAnim.animations = [scaleAnim, alphaAnim]
        groupAnim.duration = 0.6
        groupAnim.fillMode = .forwards
        groupAnim.isRemovedOnCompletion = false
        rippleLayer?.add(groupAnim, forKey: "ripple")
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)
        clearRipple()
    }
    
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesCancelled(touches, with: event)
        clearRipple()
    }
    
    private func clearRipple() {
        rippleLayer?.removeAllAnimations()
        rippleLayer?.removeFromSuperlayer()
        rippleLayer = nil
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupBaseStyle()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupBaseStyle()
    }
    
    private func setupBaseStyle() {
        backgroundColor = .systemGray6
        layer.cornerRadius = 8
        setTitle("波纹按钮", for: .normal)
        setTitleColor(.systemBlue, for: .normal)
        clipsToBounds = true
    }
}

该实现能模拟系统按钮的波纹扩散触感，提升交互细腻度。

内容的提问来源于stack exchange，提问作者Cheok Yan Cheng