Question

一个简单的问题，但我没有得到满意的答案。因此，我想通过代码向我添加的UIViewController添加一些约束。

非常感谢您：)

override func viewDidLoad() {

let imageLogoName = "pictureIsInAssets"
let imageLogo = UIImage(named: imageLogoName)
let imageLogoView = UIImageView(image: imageLogo!)

setImageContraints()
}



func setImageContraints(){

imageLogoView.translatesAutoresizingMaskIntoConstraints = false
imageLogoView.widthAnchor.constraint(equalToConstant: 180).isActive = true
imageLogoView.heightAnchor.constraint(equalToConstant: 180).isActive = true
imageLogoView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
imageLogoView.centerYAnchor.constraint(equalTo: view.centerYAnchor, constant: 28).isActive = true
    }

在func setImageContraints中：错误：使用无法解析的标识符“ imageLogoView”

Answer 1

您在可见性/生命周期范围之外使用变量imageLogoView。您应该改为使用实例变量：

class SomeViewController {
    var imageLogoView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad() // <-- notice this

        let imageLogoName = "pictureIsInAssets"
        let imageLogo = UIImage(named: imageLogoName)
        self.imageLogoView = UIImageView(image: imageLogo!)

        setImageContraints()
    }
}

或更简单：

class SomeViewController {
    let imageLogoView = UIImageView(image: UIImage(imageLiteralResourceName: "pictureIsInAssets"))

    override func viewDidLoad() {
        super.viewDidLoad() // <-- notice this

        setImageContraints()
    }
}

不要忘记将图像视图添加到视图中。

Answer 2

imageLogoView不是全局变量。

您必须这样声明：

class ViewController: UIViewController{
   let imageLogoView: UIImageView!


   override func viewDidLoad() {

   let imageLogoName = "pictureIsInAssets"
   let imageLogo = UIImage(named: imageLogoName)
   imageLogoView = UIImageView(image: imageLogo!)

   setImageContraints()
   }
}

向UIViewController添加约束不起作用

2 个答案: