How to use CoreText to replace UILabel in Swift? - ios

Question

Currently I am using UILabel to put texts on the screen:
var label = UILabel()
view.addSubView(label)
label.backgroundColor = UIColor.whiteColor()
label.numberOfLines = 2
label.font = UIFont.systemFontOfSize(20, weight: UIFontWeightMedium)
label.frame = CGRectMake(0, 0, 100, 50)
label.text = "Hi, this is some text..."
How to use CoreText to replace the above in Swift?

Answer 1

Following code solved my question:
override func drawRect(rect: CGRect) {
super.drawRect(rect)
let context = UIGraphicsGetCurrentContext()
// Flip the coordinate system
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
let path = CGPathCreateMutable()
CGPathAddRect(path, nil, self.bounds)
let str = NSMutableAttributedString(string: "some text goes here...")
// set font color
str.addAttribute(kCTForegroundColorAttributeName as String, value:UIColor.blackColor() , range: NSMakeRange(0,str.length))
// set font name & size
let fontRef = UIFont.systemFontOfSize(20, weight: UIFontWeightMedium)
str.addAttribute(kCTFontAttributeName as String, value: fontRef, range:NSMakeRange(0, str.length))
let frameSetter = CTFramesetterCreateWithAttributedString(str)
let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil)
CTFrameDraw(ctFrame, context!)
}

Answer 2

Update for Swift 4.0:
override func draw(_ rect: CGRect) {
super.draw(rect)
// context allows you to manipulate the drawing context (i'm setup to draw or bail out)
guard let context: CGContext = UIGraphicsGetCurrentContext() else {
return
}
// Flip the coordinate system
context.textMatrix = CGAffineTransform.identity;
context.translateBy(x: 0, y: self.bounds.size.height);
context.scaleBy(x: 1.0, y: -1.0);
let path = CGMutablePath()
path.addRect(self.bounds)
let str = NSMutableAttributedString(string: "00:00:00")
// set font color
str.addAttribute(NSAttributedStringKey(rawValue: kCTForegroundColorAttributeName as String), value:UIColor.purple , range: NSMakeRange(0,str.length))
// set font name & size
let fontRef = UIFont.systemFont(ofSize: 20, weight: UIFont.Weight.bold)
str.addAttribute(NSAttributedStringKey(rawValue: kCTFontAttributeName as String), value: fontRef, range:NSMakeRange(0, str.length))
let frameSetter = CTFramesetterCreateWithAttributedString(str)
let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil)
CTFrameDraw(ctFrame, context)
}

Answer 3

Try this:
func drawText(context: CGContextRef, text: NSString, attributes: [String: AnyObject], x: CGFloat, y: CGFloat) -> CGSize {
let font = attributes[NSFontAttributeName] as UIFont
let attributedString = NSAttributedString(string: text, attributes: attributes)
let textSize = text.sizeWithAttributes(attributes)
// y: Add font.descender (its a negative value) to align the text at the baseline
let textPath = CGPathCreateWithRect(CGRect(x: x, y: y + font.descender, width: ceil(textSize.width), height: ceil(textSize.height)), nil)
let frameSetter = CTFramesetterCreateWithAttributedString(attributedString)
let frame = CTFramesetterCreateFrame(frameSetter, CFRange(location: 0, length: attributedString.length), textPath, nil)
CTFrameDraw(frame, context)
return textSize
}
And call like this:
var textAttributes: [String: AnyObject] = [
NSForegroundColorAttributeName : UIColor(white: 1.0, alpha: 1.0).CGColor,
NSFontAttributeName : UIFont.systemFontOfSize(17)
]
drawText(ctx, text: "Hello, World!", attributes: textAttributes, x: 50, y: 50)
Hope this works!

Answer 4

Updated for swift 3.0:
if let context = UIGraphicsGetCurrentContext(){
// Flip the coordinate system
context.textMatrix = CGAffineTransform.identity;
context.translateBy(x: 0, y: self.bounds.size.height);
context.scaleBy(x: 1.0, y: -1.0);
let path = CGMutablePath()
path.addRect(self.bounds)
let str = NSMutableAttributedString(string: "some text goes here...")
// set font color
str.addAttribute(kCTForegroundColorAttributeName as String, value:UIColor.black , range: NSMakeRange(0,str.length))
// set font name & size
let fontRef = UIFont.systemFont(ofSize: 20, weight: UIFontWeightMedium)
str.addAttribute(kCTFontAttributeName as String, value: fontRef, range:NSMakeRange(0, str.length))
let frameSetter = CTFramesetterCreateWithAttributedString(str)
let ctFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0,str.length), path, nil)
CTFrameDraw(ctFrame, context)
}