UISearchBar

设置UISearchBar中

• placeholder颜色
• placeholder
• 输入字体颜色
• 背景颜色
• 清除按钮颜色

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        let searchBar = UISearchBar(frame: CGRect(x: 0, y: 20, width: UIScreen.main.bounds.width, height: 44))
        searchBar.searchBarStyle = .default
        view.addSubview(searchBar)

        searchBar.placeholder = "placeholder"
        searchBar.set(textColor: .brown)
        searchBar.setTextField(color: UIColor.green.withAlphaComponent(0.3))
        searchBar.setPlaceholder(textColor: .white)
        searchBar.setSearchImage(color: .white)
        searchBar.setClearButton(color: .red)
    }
}

import UIKit

extension UISearchBar {

    func getTextField() -> UITextField? { return value(forKey: "searchField") as? UITextField }
    func set(textColor: UIColor) { if let textField = getTextField() { textField.textColor = textColor } }
    func setPlaceholder(textColor: UIColor) { getTextField()?.setPlaceholder(textColor: textColor) }
    func setClearButton(color: UIColor) { getTextField()?.setClearButton(color: color) }

    func setTextField(color: UIColor) {
        guard let textField = getTextField() else { return }
        switch searchBarStyle {
        case .minimal:
            textField.layer.backgroundColor = color.cgColor
            textField.layer.cornerRadius = 6
        case .prominent, .default: textField.backgroundColor = color
        @unknown default: break
        }
    }

    func setSearchImage(color: UIColor) {
        guard let imageView = getTextField()?.leftView as? UIImageView else { return }
        imageView.tintColor = color
        imageView.image = imageView.image?.withRenderingMode(.alwaysTemplate)
    }
}

private extension UITextField {

    private class Label: UILabel {
        private var _textColor = UIColor.lightGray
        override var textColor: UIColor! {
            set { super.textColor = _textColor }
            get { return _textColor }
        }

        init(label: UILabel, textColor: UIColor = .lightGray) {
            _textColor = textColor
            super.init(frame: label.frame)
            self.text = label.text
            self.font = label.font
        }

        required init?(coder: NSCoder) { super.init(coder: coder) }
    }


    private class ClearButtonImage {
        static private var _image: UIImage?
        static private var semaphore = DispatchSemaphore(value: 1)
        static func getImage(closure: @escaping (UIImage?)->()) {
            DispatchQueue.global(qos: .userInteractive).async {
                semaphore.wait()
                DispatchQueue.main.async {
                    if let image = _image { closure(image); semaphore.signal(); return }
                    guard let window = UIApplication.shared.windows.first else { semaphore.signal(); return }
                    let searchBar = UISearchBar(frame: CGRect(x: 0, y: -200, width: UIScreen.main.bounds.width, height: 44))
                    window.rootViewController?.view.addSubview(searchBar)
                    searchBar.text = "txt"
                    searchBar.layoutIfNeeded()
                    _image = searchBar.getTextField()?.getClearButton()?.image(for: .normal)
                    closure(_image)
                    searchBar.removeFromSuperview()
                    semaphore.signal()
                }
            }
        }
    }

    func setClearButton(color: UIColor) {
        ClearButtonImage.getImage { [weak self] image in
            guard   let image = image,
                let button = self?.getClearButton() else { return }
            button.imageView?.tintColor = color
            button.setImage(image.withRenderingMode(.alwaysTemplate), for: .normal)
        }
    }

    var placeholderLabel: UILabel? { return value(forKey: "placeholderLabel") as? UILabel }

    func setPlaceholder(textColor: UIColor) {
        guard let placeholderLabel = placeholderLabel else { return }
        let label = Label(label: placeholderLabel, textColor: textColor)
        setValue(label, forKey: "placeholderLabel")
    }

    func getClearButton() -> UIButton? { return value(forKey: "clearButton") as? UIButton }
}