Implement Keyboard Key Pop Animation in iOS 8 Keyboard Extension

Question

I\'d like to ask how to implement the pop animation when holding a keyboard key for iOS 8 keyboards extension. I know how to assign the long press gesture on every key but doesn

Answer 1

I would use a CAShapeLayer.

You can reset the shape layer's shape at any time, and even animate the change in shape to do something more elaborate than the Apple version.

Here is code for a playground that demonstrates a simple version of a class that accomplishes this:

import UIKit

class KeyPopView: UIView {

  static let widthPadding : CGFloat = 5.0
  static let leftOffset : CGFloat = -5.0

  init(frame: CGRect, letters: [String]) {
    super.init(frame: frame)
    addLetters(letters)
  }

  required init(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  override class func layerClass() -> AnyClass {
    return CAShapeLayer.self
  }

  override func layoutSubviews() {
    super.layoutSubviews()
    var run : CGFloat = KeyPopView.widthPadding
    for l in labels {
      let s = sizeForLabel(l)
      let mh = maxHeight(labels)
      l.frame = CGRectMake(run, -mh, s.width, s.height)
      run += s.width + KeyPopView.widthPadding
    }
  }

  var shapeLayer: CAShapeLayer {
    get {
      return layer as! CAShapeLayer
    }
  }

  var path: CGPathRef {
    get {
      return shapeLayer.path
    }
    set(nv) {
      shapeLayer.shadowPath = nv
      shapeLayer.path = nv
    }
  }

  var labels : [UILabel] = [] {
    willSet {
      for l in labels {
        l.removeFromSuperview()
      }
    }
    didSet {
      for l in labels {
        addSubview(l)
      }
      path = keyPopPath(labels, cornerRadius: cornerRadius).CGPath
    }
  }

  var cornerRadius : CGFloat = 4 {
    didSet {
      path = keyPopPath(labels, cornerRadius: cornerRadius).CGPath
    }
  }

  override var backgroundColor: UIColor? {
    set(newValue) {
      shapeLayer.fillColor = newValue?.CGColor
    }
    get {
      return UIColor(CGColor: shapeLayer.fillColor)
    }
  }

  func keyPopPath(ls : [UILabel], cornerRadius: CGFloat) -> UIBezierPath {
    let radius = CGSizeMake(cornerRadius, cornerRadius);
    let f = CGRectMake(0, 0, frame.width + KeyPopView.widthPadding * 2, frame.height)
    let mh = maxHeight(ls)
    var b = UIBezierPath(roundedRect: CGRectMake(KeyPopView.leftOffset, -mh, widthForLabels(ls) - KeyPopView.leftOffset + KeyPopView.widthPadding, mh), byRoundingCorners: UIRectCorner.AllCorners, cornerRadii: radius)
    b.appendPath(UIBezierPath(roundedRect: f, byRoundingCorners: UIRectCorner.BottomLeft | UIRectCorner.BottomRight, cornerRadii: radius))
    return b
  }

  func addLetters(letters : [String]) {
    labels = letters.map({(s: String) -> UILabel in
      var l = UILabel()
      l.text = s
      return l
    })
  }

  func widthForLabels(ls: [UILabel]) -> CGFloat {
    return ls.reduce(0, combine: {(t, l) in t + sizeForLabel(l).width + KeyPopView.widthPadding}) + KeyPopView.widthPadding
  }

  func sizeForLabel(l: UILabel) -> CGSize {
    return l.text!.sizeWithAttributes([NSFontAttributeName: l.font])
  }

  func maxHeight(ls: [UILabel]) -> CGFloat {
    var m : CGFloat = 0;
    for l in ls {
      let h = sizeForLabel(l).height
      m = m > h ? m : h
    }
    return m
  }
}

//start with a gray background view
var ba = UIView(frame: CGRectMake(0, 0, 300, 300))
ba.backgroundColor = UIColor.grayColor()
//add a mock "key"
let key = UILabel()
key.text = "a"
key.textAlignment = NSTextAlignment.Center
key.backgroundColor = UIColor.whiteColor()
let size = key.text!.sizeWithAttributes([NSFontAttributeName: key.font])
key.frame = CGRectMake(5, 0, size.width + 10, size.height)
key.layer.cornerRadius = 5
key.center = ba.center
ba.addSubview(key)
//add the initial keypop
key.hidden = true // the key's rounded corners aren't showing up correctly in my playground preview -- this shouldn't be necessary
var k = KeyPopView(frame: CGRectMake(0, 0, size.width, size.height), letters: ["a"])
k.backgroundColor = UIColor.whiteColor()
ba.addSubview(k)
k.center = CGPointMake(key.center.x - 5, key.center.y)
ba
//demonstrates resizing of the keypop view to accomdate more letters
k.addLetters(["a", "b", "c", "d", "e"])
ba

In its current form, this class has many issues:

• Letters are slightly off center
• The frame of the view is used as the frame of the key that the pop begins from, not the actual frame of what is drawn.
• It only supports left key pops
• Several optionals are force unwrapped
• The "stem" of the path used doesn't have rounded inner corners like the System Keyboard
• Variables are named for brevity, not clarity

however this should provide a good basis for achieving what you want.