• What is the properties about shadow
    • They are properties of CALayer
    • shadowColor
      • CGColor
    • shadowOpacity
      • [0, 1], 0 -> transparent, 1 -> opaque
      • 0 by default -> your shadow is not shown by default
    • shadowOffset
      • Offset: CGSize
      • When set to (0, 0), it is four boarder shadow
      • When set to (width, height), shadow.x += width, shdow.y += height
    • shadowRadius
      • Blend
    • shadowPath
      • Shadow will draw in this path if not nil, using properties from shadowOpacity, shadowOffset, shadowRadius, shadowColor
  • How can you implement common shadow
    • Set the four properties 
      let workView = UIView(frame: CGRect(x: 100, y: 100, width: 100, height: 100))
        workView.backgroundColor = UIColor.red
        workView.layer.shadowColor = UIColor.green.cgColor
        workView.layer.shadowOpacity = 1
        workView.layer.shadowOffset = CGSize(width: 10, height: 10)
        workView.layer.shadowRadius = 5
  • How can you implement custom shadow
    • Set the four properties
    • New a path, and set to shadowPath let bezierPath = UIBezierPath() 
              bezierPath.move(to: CGPoint(x: 0, y: 0))
        bezierPath.addLine(to: CGPoint(x: 0, y: 200))
        bezierPath.addLine(to: CGPoint(x: 100, y: 200))
        bezierPath.addLine(to: CGPoint(x: 100, y: 0))
        bezierPath.close()
        
        workView.layer.shadowPath = bezierPath.cgPath
  • How can you implement shadow on round corner view
    • When clipsToBounds is set true, the layer.maskToBounds is also set to true
      • Set layer.maskToBounds back to fasle will show the shadow
    • New a new transparent view and place the origin view into it as a subview
      • Set shadow to the new view
      • Not recommended
  • What if you have three views and you want to add the same shadow to them?
    • Put them into the same tranparent view
    • Set shadow to the parent view