NSMutableAttributedString中的NSTextAttachment垂直对齐 [英] Vertically aligning NSTextAttachment in NSMutableAttributedString

问题描述

我正在像这样在NSMutableAttributedString中使用NSTextAttachment向UILabel添加图标:

I'm adding an icon to a UILabel using NSTextAttachment inside an NSMutableAttributedString like this:

//Setting up icon
let moneyIcon = NSTextAttachment()
moneyIcon.image = UIImage(named: "MoneyIcon")
let moneyIconString = NSAttributedString(attachment: moneyIcon)

//Setting up text
let balanceString = NSMutableAttributedString(string: " 1,702,200")
balanceString.insert(moneyIconString, at: 0)

//Adding string to label
self.attributedText = balanceString
self.sizeToFit()

但是由于某种原因，图标未垂直对齐

But for some reason the icon isn't vertically aligned

有人知道我如何对齐它吗?

Does anybody know how can I align it?

谢谢！

推荐答案

此答案，即将两个垂直居中单个NSAttributedString中大小不同的字体，提到使用基线偏移量来计算字符串的中心.

This answer, which is about vertically centering two differently sized fonts in a single NSAttributedString, mentions using the baseline offset to calculate the center of the string.

使用图像时可以使用相同的方法:

You can use the same approach when using an image:

1. 从图像高度中减去字体大小，然后将其除以2.

1. Subtract the font size from the image's height and divide it by 2.

从该值中减去字体的降序(因为字体大小与字体的升序不同).您特别使用的字体( Baloo-Regular )的降序值不同于标准字体，应除以2.其他字体(包括San Fransisco)不需要此修复程序或要求使用其他除数.

Subtract the font's descender from the value (since font size isn't the same as the ascent of your font). The font that you are particularly using (Baloo-Regular) has a descender value that differs from the standard and it should be divided by 2. Other fonts (including San Fransisco) don't need that fix or require a different divisor.

此代码涵盖了大多数情况，如果字体的行为不同，则应签出

This code covers most cases, if your font behaves differently, you should check out the guide for managing texts in Text Kit.

// *Setting up icon*

let moneyIcon = NSTextAttachment()

// If you're sure a value is not and will never be nil, you can use "!".
// Otherwise, avoid it.

let moneyImage = UIImage(named: "MoneyIcon")!

moneyIcon.image = moneyImage
let moneyIconString = NSAttributedString(attachment: moneyIcon)

// *Setting up NSAttributedString attributes*

let balanceFontSize: CGFloat = 16

let balanceFont = UIFont(name: "Baloo", size: balanceFontSize)!

let balanceBaselineOffset: CGFloat = {
    let dividend =  moneyImage.size.height - balanceFontSize

    return dividend / 2 - balanceFont.descender / 2
}()

let balanceAttr: [NSAttributedString.Key: Any] = [
    .font: balanceFont,
    .baselineOffset: balanceBaselineOffset
]

// *Setting up text*

let balanceString = NSMutableAttributedString(
    string: " 1,702,200",
    attributes: balanceAttr
)

balanceString.insert(moneyIconString, at: 0)

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