单击按钮更改背景图像

Question

我可以像这样在viewDidLoad功能上更改背景图像：

    let myBackgroundImage = UIImageView (frame: UIScreen.main.bounds)
    myBackgroundImage.image = UIImage(named: "wallpaper-1-iphone-8-plus.png")
    myBackgroundImage.contentMode = UIViewContentMode.scaleAspectFill
    self.view.insertSubview(myBackgroundImage, at: 0)

我想做同样的动作，按一下按钮，如下所示：

    @IBAction func flip4btn5(_ sender: Any)
{
    let myBackgroundImage = UIImageView (frame: UIScreen.main.bounds)
    myBackgroundImage.image = UIImage(named: "wallpaper-2-iphone-8-plus.png")
    myBackgroundImage.contentMode = UIViewContentMode.scaleAspectFill
    self.view.insertSubview(myBackgroundImage, at: 0)
}

但它不会改变背景图像。为什么？你觉得呢？

我在用Swift 4.1。

Answer 1

试试这段代码，它运行得很好。

class ViewController: UIViewController {

    var myBackgroundImage = UIImageView (frame: UIScreen.main.bounds);

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        myBackgroundImage.image = UIImage(named: "wallpaper-1-iphone-8-plus.png")
        myBackgroundImage.contentMode = UIViewContentMode.scaleAspectFill
        self.view.insertSubview(myBackgroundImage, at: 0)
    }

    @IBAction func flip4btn5(_ sender: UIButton) {
        myBackgroundImage.image = UIImage(named: "wallpaper-2-iphone-8-plus.png")    
    }    
}

Answer 2

不要创造新的形象。只需更改按钮中第一个UIImage的图片，如下所示：

myBackgroundImage.image = UIImage(named: "wallpaper-2-iphone-8-plus.png")

Answer 3

不要每次想要更改背景图像时都添加UIImageViews。

将UIImageView放在需要它的视图层次结构中，并保持对它的引用。然后根据需要在其上设置图像属性。

class ViewController: UIViewController {

   @IBOutlet weak var backgroundImageView: UIImageView!

   override func viewDidLoad() {
        super.viewDidLoad()

        backgroundImageView.image = UIImage(named: "wallpaper-1-iphone-8-plus.png")
   }

   @IBAction func flip4btn5(_ sender: Any) {
       backgroundImageView.image = UIImage(named: "wallpaper-2-iphone-8-plus.png")
   }
}

您可以在故事情节提要或contentMode中设置viewDidLoad。您不需要在更新图像之后继续设置它。