UIButton not working loaded in a child ViewController - ios

Question

I've got a MainViewController where I'm loading a slideout-menu. The MainViewController contains a static TopView and a ContentView where different child controllers or views are loaded, depending on which menu entry was selected.
There is a button inside one of the children is loaded, but it is not working.
When I start the app with the ViewController including the button, set to "is initial View Controller", everything works properly.
When starting the app with the MainViewController as initial View Controller with a loaded child, the button is not working (it is loaded in the view, but not reacting).
Any suggestions how I can make this work?
MainViewController loading of Child View
class MainViewController: UIViewController, SideBarDelegate {
var contentView = UIView()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
....
contentView.backgroundColor = UIColor(red: 70/255, green: 174/255, blue: 253/255, alpha: 1)
contentView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(contentView)
contentView.topAnchor.constraint(equalTo: statusBarView.bottomAnchor).isActive = true
contentView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
contentView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
contentView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
contentView.layoutIfNeeded()
}
func sideBarDidSelectButtonAtIndex(_ index: Int) {
...
if index == 0{
statusBarLabel.text = "First"
let controller:FirstViewController = storyboard!.instantiateViewController(withIdentifier: "First") as! FirstViewController
controller.view.frame = ContentView.bounds
controller.willMove(toParentViewController: self)
contentView.addSubview(controller.view)
controller.didMove(toParentViewController: self)
print("touched index 0")
} else if index == 1{
// index is 1
}
}
FirstViewController
class FirstViewController: UIViewController, UIScrollViewDelegate {
let addButton = UIButton()
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor(red: 230/255, green: 230/255, blue: 230/255, alpha: 1)
addButton.frame = CGRect(x: 0, y: 0, width: self.view.frame.size.width, height: 60)
addButton.clipsToBounds = true
addButton.setTitleColor(UIColor.white, for: .normal)
addButton.backgroundColor = UIColor(red: 102/255, green: 204/255, blue: 255/255, alpha: 1)
addButton.setTitle("add feed", for: .normal)
addButton.titleLabel?.font = UIFont.systemFont(ofSize: 20, weight: UIFontWeightRegular)
self.view.addSubview(AddButton)
addButton.layoutIfNeeded()
addButton.addTarget(self, action: #selector(touchUpAddButton), for: UIControlEvents.touchUpInside)
addButton.addTarget(self, action: #selector(touchDownAddButton), for: UIControlEvents.touchDown)
func touchUpAddButton() {
addButton.backgroundColor = UIColor(red: 102/255, green: 204/255, blue: 255/255, alpha: 1)
}
func touchDownAddButton() {
addButton.backgroundColor = UIColor(red: 70/255, green: 174/255, blue: 253/255, alpha: 1)
}
}

Answer 1

While adding the view in the container you don't have to use addSubview function, that the FirstViewController functionality is not working.
Use below code:
let newViewController:FirstViewController = storyboard!.instantiateViewController(withIdentifier: "First") as! FirstViewController
let oldViewController = childViewControllers.last! as UIViewController
oldViewController.willMove(toParentViewController: nil)
addChildViewController(newViewController)
transition(from: oldViewController, to: newViewController, duration: 0.25, options: .transitionCrossDissolve, animations:{ () -> Void in
// nothing needed here
}, completion: { (finished) -> Void in
oldViewController.removeFromParentViewController()
newViewController.didMove(toParentViewController: self)
})
You can change the duration, it used for animation

Answer 2

Update your functions to these
func TouchUpAddButton(sender: UIButton){
addButton.backgroundColor = UIColor(red: 102/255, green: 204/255, blue: 255/255, alpha: 1)
}
func TouchDownAddButton(sender: UIButton) {
addButton.backgroundColor = UIColor(red: 70/255, green: 174/255, blue: 253/255, alpha: 1)
}
And change your code of adding the target to
addButton.addTarget(self, action: #selector(FirstViewController.touchUpAddButton(_:)), for: .touchDown)
addButton.addTarget(self, action: #selector(FirstViewController.touchDownAddButton(_:)), for: .touchDown)

Answer 3

First solution:
Remove an autolayout constrains
Second solution:
Button is not performing an action because a child view controller view should be added directly to a container controller view (in your case: MainViewController view) and not via an intermediate view (in your case: contentView)