为什么 CATextLayer 将半角逗号“，”渲染为全角逗号“，”

Question

下面是代码

import UIKit
let view = UIView(frame: CGRect(x: 0, y: 0, width: 500, height: 500))
let txtLayer = CATextLayer()
txtLayer.frame = CGRect(x: 10, y: 10, width: 150, height: 50)
txtLayer.foregroundColor = UIColor.red.cgColor
txtLayer.string = ",，"
txtLayer.contentsScale = UIScreen.main.scale

view.layer.addSublayer(txtLayer)
let b = UILabel(frame: CGRect(x: 10, y: 90, width: 40, height: 20))
b.text = ",，"
b.textColor = UIColor.red
view.addSubview(b)

我想 CATextLayer 渲染“，”，如 UILabel 以显示正确的符号“，”，而不是“，”。 我能怎么做？

Answer 1

CATextLayer和UILabel默认使用不同的字体。 您可以通过打印它们的font属性来看到这一点：

print(txtLayer.font!)
print(b.font!)

这会为我打印这些：

<UICTFont: 0x7fe3718061d0> font-family: "Helvetica"; font-weight: normal; font-style: normal; font-size: 36.00pt
<UICTFont: 0x7fe371909400> font-family: ".SFUI-Regular"; font-weight: normal; font-style: normal; font-size: 17.00pt

如果您将它们都设置为相同的字体和相同的大小以使其更加明显，您会看到它们显示的文本看起来完全一样。

let view = UIView(frame: CGRect(x: 0, y: 0, width: 500, height: 500))
let txtLayer = CATextLayer()
txtLayer.frame = CGRect(x: 10, y: 10, width: 150, height: 100)
txtLayer.foregroundColor = UIColor.red.cgColor
txtLayer.string = ",，"
txtLayer.contentsScale = UIScreen.main.scale
txtLayer.font = UIFont.systemFont(ofSize: 50) as CTFont
txtLayer.fontSize = 50

view.layer.addSublayer(txtLayer)
let b = UILabel(frame: CGRect(x: 10, y: 140, width: 150, height: 100))
b.text = ",，"
b.textColor = UIColor.red
b.font = .systemFont(ofSize: 50)
view.addSubview(b)