在所有ViewControllers Swift iOS 11中添加背景图像的最佳实践

Question

Previously on ios 10 I hade the following code which works perfect for me. I just added UIView with UIImage + UIView with specific colour. After testing it on ios 11 I found out that some of the screens have this ImageView on top of the rest UI elements, so whats wrong with that

 override func viewDidLoad() {
    super.viewDidLoad()

    configureView()
}

func configureView() {
    view.backgroundColor = UIColor.clear
    let backgroundImage = getBackgroundImage()
    view.addSubview(backgroundImage)
    view.sendSubview(toBack: backgroundImage)
}

func getBackgroundImage() -> UIView {
    let backgroundImage = UIImageView(frame: UIScreen.main.bounds)
    backgroundImage.image = UIImage(named: "lemons")
    backgroundImage.contentMode =  UIViewContentMode.scaleAspectFill

    let backgroundView = UIView(frame: UIScreen.main.bounds)
    backgroundView.backgroundColor = black
    backgroundImage.addSubview(backgroundView)

    return backgroundImage
}

Answer 1

If you're creating your view controller programmatically (meaning no storyboard or nib), you can add a background image very simply like this:

class SomeViewController: UIViewController {

    override func loadView() {
        view = UIView()
        view.frame = UIScreen.main.bounds
        setBackground()
    }

    func setBackground() {

        // set image
        let bg = UIImageView()
        bg.image = // some UIImage
        bg.frame = view.bounds
        bg.contentMode = .scaleAspectFill
        bg.clipsToBounds = true
        view.insertSubview(bg, at: 0)

        // set tint
        let tint = UIView()
        tint = view.bounds
        tint = UIColor.red
        tint = 0.5
        view.insertSubview(tint, at: 1)

    }

}

Remember, when you create a view controller programmatically, you must create the view controller's actual view, ie view = UIView() . Furthermore, "core" tasks, like setting a background image, should be done in loadView and "finishing-touch" tasks, or tasks that you want to be executed after the view controller has loaded itself entirely into memory, should be executed in viewDidLoad . And, of course, configuring the view controller's view property should definitely not be left for last.

Answer 2

Move configureView() call from viewDidLoad into viewWillLayoutSubviews . The latter is inconvenient in that it is called many times in the course of the view controller's life, so use a Bool property to check, so that you only call configureView() once , the very first time.

Answer 3

Swift 4:

Better to keep it in helper class:

static func setBlurBackGround(_ vc:UIViewController){
        let imageView = UIImageView()
        imageView.image = #imageLiteral(resourceName: "BackGround")
        imageView.frame = dBounds
        vc.view.addSubview(imageView)
    }