KeyboardViewController.swift source from AppDesignVault for Swift 3

KeyboardViewController.swift

//
//  KeyboardViewController.swift
//  Demo Custom Keyboard
//
//  Created by Drew Lustro on 10/20/14.
//  Updated by Jared Bigcraft on 10/29/2016 to work with Swift 3
//
//  Original derived from tutorial found on AppDesignVault
//  http://www.appdesignvault.com/ios-8-custom-keyboard-extension/
//
//
// *** ALL AUTOLAYOUT CONSTRAINTS HAVE BEEN FIXED! ;) NO MORE WARNINGS
//
//  https://gist.github.com/drewlustro/641d5844e43e87d0c011
//  https://gist.github.com/critical186/4c05e2700fd233507ef1460bd8d969f7
//
import UIKit

class KeyboardViewController: UIInputViewController {
    
    override func updateViewConstraints() {
        super.updateViewConstraints()
        
        // Add custom view sizing constraints here
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let buttonTitles1 = ["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"]
        let buttonTitles2 = ["A", "S", "D", "F", "G", "H", "J", "K", "L"]
        let buttonTitles3 = ["CP", "Z", "X", "C", "V", "B", "N", "M", "BP"]
        let buttonTitles4 = ["CHG", "SPACE", "RETURN"]
        
        let row1 = createRowOfButtons(buttonTitles: buttonTitles1 as [NSString])
        let row2 = createRowOfButtons(buttonTitles: buttonTitles2 as [NSString])
        let row3 = createRowOfButtons(buttonTitles: buttonTitles3 as [NSString])
        let row4 = createRowOfButtons(buttonTitles: buttonTitles4 as [NSString])
        
        self.view.addSubview(row1)
        self.view.addSubview(row2)
        self.view.addSubview(row3)
        self.view.addSubview(row4)
        
        row1.translatesAutoresizingMaskIntoConstraints = false
        row2.translatesAutoresizingMaskIntoConstraints = false
        row3.translatesAutoresizingMaskIntoConstraints = false
        row4.translatesAutoresizingMaskIntoConstraints = false
        
        addConstraintsToInputView(inputView: self.view, rowViews: [row1, row2, row3, row4])
    }
    
    func createRowOfButtons(buttonTitles: [NSString]) -> UIView {
        
        var buttons = [UIButton]()
        let keyboardRowView = UIView(frame: CGRect(x:0, y:0, width:320, height:50))
        //        keyboardRowView.tag = self.rowCount++
        
        for buttonTitle in buttonTitles {
            
            let button = createButtonWithTitle(title: buttonTitle as String)
            buttons.append(button)
            keyboardRowView.addSubview(button)
        }
        
        addIndividualButtonConstraints(buttons: buttons, rowView: keyboardRowView)
        
        return keyboardRowView
    }
    
    func createButtonWithTitle(title: String) -> UIButton {
        
        let button = UIButton.init(type: .system) as UIButton
        button.frame = CGRect(x:0, y:0, width:20, height:20)
        button.setTitle(title, for: .normal)
        button.sizeToFit()
        button.titleLabel?.font = UIFont.systemFont(ofSize: 15)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.backgroundColor = UIColor(white: 1.0, alpha: 1.0)
        button.setTitleColor(UIColor.darkGray, for: .normal)
        
        button.addTarget(self, action:#selector(didTapButton(_:)), for: .touchUpInside)
        
        return button
    }
    
    func didTapButton(_ sender: AnyObject?) {
 
        let button = sender as! UIButton
        
        let proxy = textDocumentProxy as UITextDocumentProxy
        print("Pressed:\(button.title(for: .normal) as String?)")
        
        if let title = button.title(for: .normal) as String? {
            switch title {
            case "BP":
                proxy.deleteBackward()
            case "RETURN":
                proxy.insertText("\n")
            case "SPACE":
                proxy.insertText(" ")
            case "CHG":
                self.advanceToNextInputMode()
            default:
                //print("default Title:\(title)")
                proxy.insertText(title)
            }
        }
    }

    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 as UITextDocumentProxy
        //if proxy.keyboardAppearance == UIKeyboardAppearance.dark {
        //    textColor = UIColor.white
        //} else {
        //    textColor = UIColor.black
        //}
        
        
    }
    
    func addIndividualButtonConstraints(buttons: [UIButton], rowView: UIView){
        
        for (index, button) in buttons.enumerated() {
            
            let topConstraint = NSLayoutConstraint(item: button, attribute: .top, relatedBy: .lessThanOrEqual, toItem: rowView, attribute: .top, multiplier: 1.0, constant: 1.0)
            let bottomConstraint = NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .greaterThanOrEqual, toItem: rowView, attribute: .bottom, multiplier: 1.0, constant: -1.0)
            
            var rightConstraint : NSLayoutConstraint!
            
            if index == buttons.count - 1 {
                
                rightConstraint = NSLayoutConstraint(item: button, attribute: .right, relatedBy: .greaterThanOrEqual, toItem: rowView, attribute: .right, multiplier: 1.0, constant: 0.0)
                
            } else {
                
                let nextButton = buttons[index+1]
                rightConstraint = NSLayoutConstraint(item: button, attribute: .right, relatedBy: .equal, toItem: nextButton, attribute: .left, multiplier: 1.0, constant: -1.0)
            }
            
            
            var leftConstraint : NSLayoutConstraint!
            
            if index == 0 {
                
                leftConstraint = NSLayoutConstraint(item: button, attribute: .left, relatedBy: .lessThanOrEqual, toItem: rowView, attribute: .left, multiplier: 1.0, constant: 0.0)
                
            } else {
                
                let prevtButton = buttons[index-1]
                leftConstraint = NSLayoutConstraint(item: button, attribute: .left, relatedBy: .equal, toItem: prevtButton, attribute: .right, multiplier: 1.0, constant: 1.0)
                
                let firstButton = buttons[0]
                let widthConstraint = NSLayoutConstraint(item: firstButton, attribute: .width, relatedBy: .equal, toItem: button, attribute: .width, multiplier: 1.0, constant: 0.0)
                
                widthConstraint.priority = 800.0
                rowView.addConstraint(widthConstraint)
            }
            
            rowView.addConstraints([topConstraint, bottomConstraint, rightConstraint, leftConstraint])
        }
    }
    
    func addConstraintsToInputView(inputView: UIView, rowViews: [UIView]){
        
        for (index, rowView) in rowViews.enumerated() {
            
            let rightSideConstraint = NSLayoutConstraint(item: rowView, attribute: .right, relatedBy: .equal, toItem: inputView, attribute: .right, multiplier: 1.0, constant: 0.0)
            let leftConstraint = NSLayoutConstraint(item: rowView, attribute: .left, relatedBy: .equal, toItem: inputView, attribute: .left, multiplier: 1.0, constant: 0.0)
            
            inputView.addConstraints([leftConstraint, rightSideConstraint])
            
            var topConstraint: NSLayoutConstraint
            
            if index == 0 {
                topConstraint = NSLayoutConstraint(item: rowView, attribute: .top, relatedBy: .equal, toItem: inputView, attribute: .top, multiplier: 1.0, constant: 0.0)
            } else {
                
                let prevRow = rowViews[index-1]
                topConstraint = NSLayoutConstraint(item: rowView, attribute: .top, relatedBy: .equal, toItem: prevRow, attribute: .bottom, multiplier: 1.0, constant: 0.0)
                
                let firstRow = rowViews[0]
                let heightConstraint = NSLayoutConstraint(item: firstRow, attribute: .height, relatedBy: .equal, toItem: rowView, attribute: .height, multiplier: 1.0, constant: 0.0)
                
                heightConstraint.priority = 800.0
                inputView.addConstraint(heightConstraint)
            }
            inputView.addConstraint(topConstraint)
            
            var bottomConstraint: NSLayoutConstraint
            
            if index == (rowViews.count - 1) {
                bottomConstraint = NSLayoutConstraint(item: rowView, attribute: .bottom, relatedBy: .equal, toItem: inputView, attribute: .bottom, multiplier: 1.0, constant: 0.0)
                
            } else {
                
                let nextRow = rowViews[index+1]
                bottomConstraint = NSLayoutConstraint(item: rowView, attribute: .bottom, relatedBy: .equal, toItem: nextRow, attribute: .top, multiplier: 1.0, constant: 0.0)
            }

            inputView.addConstraint(bottomConstraint)
        }
    }
}

Here is the old version:
https://gist.github.com/drewlustro/641d5844e43e87d0c011