Why does my UIButton remain after a segue?

Question

I've been experimenting and practicing building apps programmatically and just can't understand why my UIButton from the root VC remains in the next view after a modal segue. When I did it through the storyboard, all of the elements in the view would disappear.

My rootVC is made of one layer and a UIButton over it:

pressing the button modally presents the next view controller, but the UIButton remains:

There are no references to the UIButton in the second VC file. Here's the code from the rootVC:

var imInChinaButton : UIButton {
        var button = UIButton( frame: CGRect(
            x: 0,
            y: 0,
            width: 300,
            height: 300))
        button.setImage(#imageLiteral(resourceName: "button"), for: .normal)
        button.setTitle("hello", for: .normal)
        button.contentMode = UIViewContentMode.scaleAspectFit
        button.center = view.center
        button.backgroundColor = .clear
        button.isUserInteractionEnabled = true
        button.addTarget(self, action: #selector(buttonTapped), for: .touchUpInside)

        return button
    }

    self.view.addSubview(imInChinaButton)
}

@objc func buttonTapped(_ sender: UIButton) {
    sender.setImage(#imageLiteral(resourceName: "pressedButton"), for: .normal)
    let resultsViewController = ResultsViewController()
    self.navigationController!.present(resultsViewController, animated: true, completion: nil)
}

Any help would be awesome! Thank you so much for your time.

Answer 1

You need to change background of modal , in viewDidLoad

self.view.backgroundColor = .red

//

If you no longer need the backVC , you can

UIApplication.shared.keyWindow?.rootViewController =  ResultsViewController()

but hiding temporarily is not possible you can do this to hide them before present but it's not a good practise

self.view.subviews.forEach { $0.isHidden = true } 

the best thing is to change the backgroundColor or completely clear the old rootVC