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##lecture 4

####View

UIWindow -> 除非有external screen，否则就一直就只有一个UIView，感觉只要是用Storyboard的就不用管这些。

addSubview(aView: UIView) // sent to aView's superview
removeFromSuperView //sent to the view you want to remove

CG

CGFloat draw的时候用，CG（core graphics）Float

CGPoint x，y

CGSize width, height

CGRect 相对的methods要多一些

Coordinate System

Coordinate System : 跟一般的Coordinate System差不多，画的时候用Point，而不是pixel，感觉是pixel independent的变体.

contentScaleFactor -> how many pixels per point

bounds : CGRect

center : 同样是superview

frame : superview's coordinate system

感觉这两个方法还是非常make sense的，因为确定其在其superview中的位置，再用bounds.

frame 和 bounds不同之处还有比如rotate 一个view具有的bounds和frame 就不一样

####Create View via code:

let newView = UIView(frame: myViewFrame)
let newView = UIView()

用代码的方法来创建一个UILabel

let labelRect = CGRect(x:20, y:20, width: 100, height:  50)
let label = UILabel(frame:labelRect)
label.text = "Hello"
view.addSubview(label)

Draw

override func drawRect(regionThatNeedsToBeDrawn: CGRect)

never call drawRect！

call

setNeedsDisplay()
setNeedsDisplayInRect(regionThatNeedsToBeDrawn: CGRect)

画一个三角形的典型code

let path = UIBezierPath()

path.moveToPoint(CGPoint(x: 80,y: 50))
path.addLineToPoint(CGPoint(x: 140,y: 150))
path.addLineToPoint(CGPoint(x: 10,y: 150))

path.closePath()

UIColor.greenColor().setFill()
UIColor.redColor().setStroke()
path.lineWidth = 3.0
path.fill()
path.stroke()

别的方法

let roundRect = UIBezierPath(roundedRect: aCGRect, cornerRadius: aCGFloat) 
let oval = UIBezierPath(ovalInRect: aCGRect)

addClip()

For example, you could clip to a rounded rect to enforce the edges of a playing card

待读，比如做cards游戏

Hit detection

func containsPoint(CGPoint) -> Bool // returns whether the point is inside the path

The path must be closed. The winding rule can be set with usesEvenOddFillRule property.

UIColor

You can also create them from RGB, HSB or even a pattern (using UIImage)

用pattern，听起来好🐂的样子。

greenColor() 是type method，用它来取得instance，所以colorWith...就是instance method.

透明度

let transparentYellow = UIColor.yellowColor().colorWithAlphaComponent(0.5) 
var opaque = false
//Alpha is between 0.0 (fully transparent) and 1.0 (fully opaque)

整个view都可以是transparent的.

不过transparency比较昂贵，使用可注意

fade out/ fade in 用alpha

var hidden : Bool

当点击某个button的时候

Draw Text

let text = NSAttributedString(“hello”)
text.drawAtPoint(aCGPoint)
let textSize: CGSize = text.size

注意是upper left开始.

NSAttributedString 感觉老是都有点不知道如何待ta.

Font

user内容-> 选preferredFont

class func preferredFontForTextStyle(UIFontTextStyle) -> UIFont

UIFontTextStyle.Headline
UIFontTextStyle.Body
UIFontTextStyle.Footnote

Draw Image

这个就是UIImageView的使用.

let image: UIImage = ...
image.drawAtPoint(aCGPoint) // the upper left corner of the image put at 	aCGPoint image.drawInRect(aCGRect) // scales the image to fit aCGRect 	image.drawAsPatternInRect(aCGRect) // tiles the image into aCGRect

可以试试patten

Redraw on bounds change

Demo

在demo过程有很有意思的做法，就是在init阶段尝试调用自己的bounds失败，是因为这个时候这个UIView自身并没有初始化完成，所以调用bounds会报错，UIView doesn't have instance variable bounds，所以这个时候的做法是把这个skullRadius改成computed property，而是是read only的，只有return.