How do you make a background image scale to screen size in swift?

Question

I\'m trying to make a UIView image for my background in swift using pattern image. The code I have works well except for the fact that I want the image to take the whole scr

Answer 1

I used constraints to make the image "autoLayout". I made a view to show an activity indicator (with full background image), while the view on segue is loading. The code is as follows.

var containerView: UIView = UIView()
var actionIndicator: UIActivityIndicatorView = UIActivityIndicatorView()

private func showActivityIndicator() {
    ///first I set the containerView and the background image
    containerView.translatesAutoresizingMaskIntoConstraints = false
    self.view.addSubview(containerView)
    adjustConstFullSize(containerView, parentView: self.view)
    let backImage = UIImageView(image: UIImage(named: "AppBackImage"))
    backImage.contentMode = UIViewContentMode.ScaleAspectFill
    backImage.translatesAutoresizingMaskIntoConstraints = false
    containerView.addSubview(backImage)
    adjustConstFullSize(backImage, parentView: containerView)

    ////setting the spinner (activity indicator)
    actionIndicator.frame = CGRectMake(0.0, 0.0, 40.0, 40.0)
    actionIndicator.center = CGPointMake(containerView.bounds.size.width / 2, containerView.bounds.size.height / 2)
    actionIndicator.hidesWhenStopped = true
    actionIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.WhiteLarge
    containerView.insertSubview(actionIndicator, aboveSubview: backImage)

    ///throw the container to the main view
    view.addSubview(containerView)
    actionIndicator.startAnimating()
}

This is the code for the "adjustConstFullSize" function.

func adjustConstFullSize(adjustedView: UIView!, parentView: UIView!) {
    let topConstraint = NSLayoutConstraint(item: adjustedView,
        attribute: .Top,
        relatedBy: .Equal,
        toItem: parentView,
        attribute: .Top,
        multiplier: 1.0,
        constant: 0.0)

    let leftConstraint = NSLayoutConstraint(item: adjustedView,
        attribute: .Leading,
        relatedBy: .Equal,
        toItem: parentView,
        attribute: .Leading,
        multiplier: 1.0,
        constant: 0.0)

    let rightConstraint = NSLayoutConstraint(item: adjustedView,
        attribute: .Trailing,
        relatedBy: .Equal,
        toItem: parentView,
        attribute: .Trailing,
        multiplier: 1.0,
        constant: 0.0)


    let bottomConstraint = NSLayoutConstraint(item: adjustedView,
        attribute: .Bottom,
        relatedBy: .Equal,
        toItem: parentView,
        attribute: .Bottom,
        multiplier: 1.0,
        constant: 0.0)

    parentView.addConstraints([topConstraint, leftConstraint, rightConstraint, bottomConstraint])
}

In the function shown above, I "tied" the containerView constraints to the main view constraints, making the view "full size". I did the same for the UIImageView and also set the contentMode to AspectFill - this is crucial, because we want the image to fill the content without stretching.

To remove the view, after the lazy loading, just use the code below.

private func hideActivityIndicator() {
    actionIndicator.stopAnimating()
    containerView.removeFromSuperview()
}