iOS8 Swift custom-keyboard button UIimage size problems

Question

I'm trying to create an iOS8 custom keyboard with swifts. So far my app is running well, I just have problems with the size of my UIImage buttons. I'm setting the keyboard size with the following method to 100 pixel:

override func viewDidAppear(animated: Bool) {
  super.viewDidAppear(animated)
  view.addConstraint(NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy:.Equal, toItem:self.view,
  attribute:.Height, multiplier:0.0, constant: 100))

And then I add the key buttons in the following way:

let image = UIImage(named: "key1.jpg")
nextKeyboardButton = UIButton.buttonWithType(.System) as UIButton
nextKeyboardButton.setBackgroundImage(image, forState: UIControlState.Normal)
// initialize the button
nextKeyboardButton.sizeToFit()
self.nextKeyboardButton.addTarget(self, action: "advanceToNextInputMode", forControlEvents: .TouchUpInside)
self.view.addSubview(self.nextKeyboardButton)
var nextKeyboardButtonLeftSideConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
var nextKeyboardButtonBottomConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
self.view.addConstraints([nextKeyboardButtonLeftSideConstraint, nextKeyboardButtonBottomConstraint])

My key1.jpg is exact 100 pixel high. It does fit exactly into the size of my keyboard area (Height = 100), but both is much to big. So it seems that each pixel taxes 2 pixel of the real retina resolution or more. Also the width is much to much. I tested with a 400 pixel wide key and just around the half fits on the screen. I also tried with an .png file, same result. There must be some general settings wrong, but I really have no idea what.

Checking the error output I got the following message:

Unable to simultaneously satisfy constraints.
    ... 
(
    "<NSLayoutConstraint:0x1700913f0 'UIView-Encapsulated-Layout-Height' V:[UIInputView:0x13f5091e0(216)]>",
    "<NSLayoutConstraint:0x170091d00 V:[UIInputView:0x13f5091e0(100)]>"
)

I did set the high to 100, but where does the high of 216 come from?

Here how it looks like

_{(source: modellautos24.de)}

and it should look like that

Answer 1

The problem is written in the log:

Unable to simultaneously satisfy constraints.
    ... 
(
    "<NSLayoutConstraint:0x1700913f0 'UIView-Encapsulated-Layout-Height' V:[UIInputView:0x13f5091e0(216)]>",
    "<NSLayoutConstraint:0x170091d00 V:[UIInputView:0x13f5091e0(100)]>"
)

You're probably setting the height using Autolayout in the Storyboard (or any other place in the code). Just remove it (or change to lower priority) and it should be set to 100px.