单击按钮更改背景图像

Question

I can change background image on viewDidLoad func like this:

    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)

i would like to do same action with button click like this:

    @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)
}

but it does not change background image. Why ? What do you think ?
I'm using Swift 4.1.

Answer 1

Don't create a new image. just change the picture of the first UIImage in your button action like this:

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

Answer 2

Don't keep adding UIImageViews everytime you want to change the background image.

Place a UIImageView in the view hierarchy where it is needed and keep a reference to it. Then set the image property on it as needed.

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")
   }
}

You can set the contentMode either in the storyboard or in viewDidLoad. You don't need to keep setting it after updating an image.

Answer 3

let myBackgroundImage = UIImageView (frame: CGRect.zero)


override func viewDidLoad() {
    super.viewDidLoad()

    myBackgroundImage.image = UIImage(named: "wallpaper-1-iphone-8-plus.png")
    myBackgroundImage.contentMode = UIViewContentMode.scaleAspectFill
    self.view.addSubview(myBackgroundImage)

}

@IBAction func ButtonPressed(_ sender: Any) {

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

}

Answer 4

Try this code, It's working fine.

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")    
    }    
}