Question

 let playButton: UIButton = {
    let button = UIButton()
    let image = UIImage(named: "VideoIcon.png") as UIImage?
    button.backgroundImage(for: .normal)
    button.addTarget(self, action: #selector(pressBackButton(button:)), for: .touchUpInside)
    button.setImage(image, for: .normal)

    return button
}()

func pressBackButton(button: UIButton) {
print("test")
    if let playVideoButtonURL = post?.videourl {

        let player = AVPlayer(url: playVideoButtonURL as URL)
        let playerLayer = AVPlayerLayer(player:player)
        playerLayer.frame = CGRect(x: 100, y: 200, width: 100, height: 100)
        playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
        self.layer.addSublayer(playerLayer)
        player.play()

    }

}

即使视频代码有误，它仍然应该打印测试，但它并不奇怪。我觉得选择器可能有问题，但我目前不知道它有什么问题。

Answer 1

在初始化程序之外访问自身的函数或属性。

class TestViewController: UIViewController {
    let playButton: UIButton = {
        let button = UIButton()
        let image = UIImage(named: "VideoIcon.png") as UIImage?
        button.backgroundImage(for: .normal)
        button.setImage(image, for: .normal)

        return button
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        button.addTarget(self, action: #selector(pressBackButton(button:)), for: .touchUpInside)
    }
}

Answer 2

而不是：

let playButton: UIButton = {

    ...
    ...
    return button
}()

哪个不起作用（因为你试图在错误的时间创建playButton - 这是在视图加载之前或即将出现之前）

在viewDidLoad或viewWillAppear中，创建按钮，定义目标并将其添加为子视图。

override func viewDidLoad() {
  super.viewDidLoad()

  let button = UIButton()
  if let image = UIImage(named: "VideoIcon.png") as UIImage?        
  {
     button.backgroundImage(for: .normal)
     button.addTarget(self, action: #selector(pressBackButton(button:)), for: .touchUpInside)
     button.setImage(image, for: .normal)
  }
  self.addSubview(button)
}

将按钮添加为子视图increments the retain count（即它不会消失），但如果您想将其保留为属性，只需将其声明为：

var playButton : UIButton?

然后在playButton = button的末尾设置viewDidLoad。

为什么没有Swift 3认出我的按钮？

2 个答案: