问用adjustsImageWhenHighlighted设置UIButtonConfiguration

EN

    // let's use new UIButton.Configuration
    newButton.configuration = .plain()
    
    newButton.configurationUpdateHandler = { button in
        var config = button.configuration
        config?.image = button.isHighlighted ? imgHighlighted : imgNormal
        button.configuration = config
    }

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
    
        guard let imgNormal = UIImage(named: "myButtonImage")
        else {
            print("Could not load images!")
            return
        }
        
        // generate a "darkened" version of the image
        let rndr = UIGraphicsImageRenderer(size: imgNormal.size)
        let imgHighlighted = rndr.image { (ctx) in
            imgNormal.draw(at: .zero)
            UIColor.black.withAlphaComponent(0.5).setFill()
            ctx.cgContext.fill(CGRect(origin: .zero, size: imgNormal.size))
        }
        
        let oldButton = UIButton()
        let newButton = UIButton()

        // "standard" button
        oldButton.setImage(imgNormal, for: [])
        // default is .adjustsImageWhenHighlighted = true
        
        // let's use new UIButton.Configuration
        newButton.configuration = .plain()
        
        newButton.configurationUpdateHandler = { button in
            var config = button.configuration
            config?.image = button.isHighlighted ? imgHighlighted : imgNormal
            button.configuration = config
        }
        
        [oldButton, newButton].forEach { b in
            b.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(b)
        }
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            
            oldButton.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            oldButton.widthAnchor.constraint(equalToConstant: 80.0),
            oldButton.heightAnchor.constraint(equalTo: oldButton.widthAnchor),
            oldButton.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            
            newButton.topAnchor.constraint(equalTo: oldButton.bottomAnchor, constant: 20.0),
            newButton.widthAnchor.constraint(equalTo: oldButton.widthAnchor),
            newButton.heightAnchor.constraint(equalTo: oldButton.widthAnchor),
            newButton.centerXAnchor.constraint(equalTo: g.centerXAnchor),
            
        ])
        
    }
    
}