API没有改变——只有语法改变了。你可以创建一个UIButton并像这样添加它:

var button = UIButton(frame: CGRectMake(0, 0, 50, 50))
self.view.addSubview(button) // assuming you're in a view controller

 func viewDidLoad(){
                    saveActionButton = UIButton(frame: CGRect(x: self.view.frame.size.width - 60, y: 0, width: 50, height: 50))
                    self.saveActionButton.backgroundColor = UIColor(red: 76/255, green: 217/255, blue: 100/255, alpha: 0.7)
                    saveActionButton.addTarget(self, action: #selector(doneAction), for: .touchUpInside)
                    self.saveActionButton.setTitle("Done", for: .normal)
                    self.saveActionButton.layer.cornerRadius = self.saveActionButton.frame.size.width / 2
                    self.saveActionButton.layer.borderColor = UIColor.darkGray.cgColor
                    self.saveActionButton.layer.borderWidth = 1
                    self.saveActionButton.center.y = self.view.frame.size.height - 80
                    self.view.addSubview(saveActionButton)
        }

          func doneAction(){
          print("Write your own logic")
         }

override func viewDidLoad() {

super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    var imageView = UIImageView(frame: CGRectMake(100, 150, 150, 150));
    var image = UIImage(named: "BattleMapSplashScreen.png");
    imageView.image = image;
    self.view.addSubview(imageView);

}

在Swift 4.2中编写下面的示例代码，用于以编程方式添加按钮。

override func viewDidLoad() {
    super.viewDidLoad()
        let myButton = UIButton(frame: CGRect(x: 100, y: 100, width: 100, height: 50))
        myButton.backgroundColor = .green
        myButton.setTitle("Hello UIButton", for: .normal)
        myButton.addTarget(self, action: #selector(myButtonAction), for: .touchUpInside)
        self.view.addSubview(myButton)
}

 @objc func myButtonAction(sender: UIButton!) {
    print("My Button tapped")
}

这是可能的。除了使用swift语法之外，您几乎可以以相同的方式完成所有操作。例如，你可以用这样的代码创建一个UIButton:

 var button: UIButton = UIButton(frame: CGRectMake(0, 0, 100, 100))

如何使用Swift 3.0来做到这一点。

func createButton() {
    let button = UIButton(type: .system)
    button.frame = CGRect(x: 100.0, y: 100.0, width: 100.0, height: 100.0)
    button.setTitle(NSLocalizedString("Button", comment: "Button"), for: .normal)
    button.backgroundColor = .green
    button.addTarget(self, action: #selector(buttonAction(sender:)), for: .touchUpInside)
    view.addSubview(button)
}

@objc func buttonAction(sender: UIButton) {
    print("Button pushed")
}