Swift 2.2 - 以编程方式初始化 UIImageView 的正确方法

Question

这个非常简单的代码（我从项目中分离出来）的失败让我不知所措。

import UIKit

class ViewController: UIViewController {

    weak var garageDoor: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        if let image = UIImage(named: "garagedoorclosed") {
            print("image ready: \(image)")
            garageDoor = UIImageView(image: image)

            print("garageDoor: \(garageDoor)")

            garageDoor.frame = CGRectMake(0, 0, 560, 400) // fails here!
            view.addSubview(garageDoor)
        }
        else {
            print("image not ready!")
        }
    }

}

我只想用名为 garagedoorclosed 的图像初始化 UIImageView。

我不知道为什么我无法用 garageDoor = UIImageView(image: image) 初始化 garageDoor。

下面是我的截图：

如有任何意见，我们将不胜感激！

谢谢

Answer 1

在 viewDidLoad 中只需替换下面的代码即可。

var garageDoor: UIImageView!

garageDoor = UIImageView(frame: CGRectMake(0, 0, 560, 400))
if let image = UIImage(named: "garagedoorclosed") {
    garageDoor.image = image
}

self.view.addSubview(garageDoor)

Answer 2

我编辑我的答案。主要问题是 garageDoor 的声明，因为 weak 意味着变量不保留对象，它将被释放。你已经删除了 weak 并且 garageDoor 会很强大。

var garageDoor: UIImageView!

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

    if let image = UIImage(named: "images2") {
        print("image ready: \(image)")

        garageDoor = UIImageView(image: image)

        print("garageDoor: \(garageDoor)")

        garageDoor.frame = CGRectMake(0, 0, 560, 400) 
        view.addSubview(garageDoor)
    }
    else {
        print("image not ready!")
    }
}

决定两个引用中哪一个应该是弱引用的经验法则：

think of the objects in the retain cycle as being in a parent-child relationship. In this relationship, the parent should maintain a strong reference (i.e., ownership of) its child, but the child should not maintain maintain a strong reference original link.

Swift 2.2 - 以编程方式初始化 UIImageView 的正确方法

Swift 2.2 - Correct way to programmatically init a UIImageView

null

initialization

uiimageview

swift2