Calculate button height of keyboard buttons - ios

Question

I'm working on a universal keyboard extension. Currently I want to calculate the height of a single button. The keyboard has 4 rows as the normal iOS keyboard. Because the space between the buttons (y distance) is 5 I calculated: (self.view.frame.height-(5*5))/4 5x5 because the distance to the top and the bottom is included. Now, if I run the app, one button isn't around 1/4 of the screen. Instead the button's height is around 2/3 of the keyboard view. I really can't find my mistake. I hope you can help me with this calculation.
My current code:
import UIKit
class KeyboardViewController: UIInputViewController, UIScrollViewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidLayoutSubviews() {
print((self.view.frame.height-25)/4)
addButtons()
}
func addButtons() {
let buttonHeigth = (self.view.frame.height-25)/4
let button = ResizableButton()
button.frame = CGRect(x: CGFloat(5), y: CGFloat(10), width: CGFloat(button.frame.size.width), height: CGFloat(buttonHeigth))
button.addTarget(self, action: #selector(keyPressed(sender:)), for: .touchUpInside)
button.layer.cornerRadius = 10
button.layer.masksToBounds = false
self.scrollView.addSubview(button)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated
}
override func textWillChange(_ textInput: UITextInput?) {
// The app is about to change the document's contents. Perform any preparation here.
}
override func textDidChange(_ textInput: UITextInput?) {
// The app has just changed the document's contents, the document context has been updated.
var textColor: UIColor
let proxy = self.textDocumentProxy
if proxy.keyboardAppearance == UIKeyboardAppearance.dark {
textColor = UIColor.white
} else {
textColor = UIColor.black
}
self.nextKeyboardButton.setTitleColor(textColor, for: [])
}
}