如何以编程方式将UIToolbar添加到iOS应用程序？

let toolbar = UIToolbar()

toolbar.frame = CGRect(x: 0, y: view.frame.height - 44, width: view.frame.width, height: 44)

toolbar.barStyle = .default

let flexSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
let barButtonItem = UIBarButtonItem(title: "按钮", style: .plain, target: self, action: #selector(buttonTapped))
toolbar.setItems([flexSpace, barButtonItem, flexSpace], animated: false)

view.addSubview(toolbar)

@objc func buttonTapped() {
    print("按钮被点击了")
}