iOS-swift - CATextLayer 绘制文字

// 1、CATextLayer比Label渲染的更快。
// 2、CATextLayer硬件加速了。
// 3、这个例子将Layer层创建成CATextLayer。重写了Label的是三个属性。
//  LayerLabel.swift
//  GATransitionAnimation
//
//  Created by houjianan on 2017/3/19.
//  Copyright © 2017年 houjianan. All rights reserved.

//  CATextLayer也要比UILabel渲染得快得多

import UIKit

class LayerLabel: UILabel {

//    API说明：The class used to create the layer for instances of this class.
    override class var layerClass: AnyClass {
        return CATextLayer.classForCoder()
    }
//    获得本身转变成CATextLayer的对象
    var textLayer: CATextLayer {
        return self.layer as! CATextLayer
    }
//    设置textLayer
    func setUp() {
        textLayer.alignmentMode = kCAAlignmentJustified
        textLayer.isWrapped = true
        
        self.layer.display()
    }
//    初始化方法
    override init(frame: CGRect) {
        super.init(frame: frame)
        setUp()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
//    xib初始化
    override func awakeFromNib() {
        setUp()
    }
//    重写相关属性text
    override var text: String? {
        didSet {
            // 001
            super.text = text
            // 002
            textLayer.string = text
        }
    }
//    重写相关属性textColor
    override var textColor: UIColor? {
        didSet {
            super.textColor = textColor
            textLayer.foregroundColor = UIColor.blue.cgColor
        }
    }
//    重写相关属性font
    override var font: UIFont? {
        didSet {
            super.font = font
            let fontRef = CGFont.init(font!.fontName as CFString)
            textLayer.font = fontRef
            textLayer.fontSize = font?.pointSize ?? 12
        }
    }
    
}