如何在 Swift 中更改 UIButton 的字母间距？答案

【问题标题】：How to change letter spacing of UIButton in Swift?如何在 Swift 中更改 UIButton 的字母间距？
【发布时间】：2015-12-02 17:12:34
【问题描述】：

我找到了如何将字母间距设置为 UILabel (here)，但此方法不适用于 UIButtons。有人知道怎么做吗？

这是我正在使用的代码

    let buttonString = agreementButton.attributedTitleForState(.Normal) as! NSMutableAttributedString
    buttonString.addAttribute(NSKernAttributeName, value: 1.0, range: NSMakeRange(0, buttonString.length))
    agreementButton.setAttributedTitle(buttonString, forState: .Normal)

它给我一个错误：'NSConcreteAttributedString' (0x19e508660) to 'NSMutableAttributedString' (0x19e506a40).

【问题讨论】：

问题到底出在哪里？请发布不适合您的代码。
已更新，让您查看损坏的代码。

标签： swift uibutton letter-spacing

【解决方案1】：

Swift 3.0

extension UIButton{
   func addTextSpacing(spacing: CGFloat){
       let attributedString = NSMutableAttributedString(string: (self.titleLabel?.text!)!)
       attributedString.addAttribute(NSKernAttributeName, value: spacing, range: NSRange(location: 0, length: (self.titleLabel?.text!.characters.count)!))
       self.setAttributedTitle(attributedString, for: .normal)
   }
}
btnRegister.addTextSpacing(spacing: 4.5)

extension UILabel{
    func addTextSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.text!)
        attributedString.addAttribute(NSKernAttributeName, value: spacing, range: NSRange(location: 0, length: self.text!.characters.count))
        self.attributedText = attributedString
    }
}
lblOne.addTextSpacing(spacing: 4.5)

extension UITextField{
    func addPlaceholderSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.placeholder!)
        attributedString.addAttribute(NSKernAttributeName, value: spacing, range: NSRange(location: 0, length: self.placeholder!.characters.count))
        self.attributedPlaceholder = attributedString
    }
}
txtUserName.addPlaceholderSpacing(spacing: 4.5)

extension UINavigationItem{
    func addSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.title!)
        attributedString.addAttribute(NSKernAttributeName, value: spacing, range: NSRange(location: 0, length: self.title!.characters.count))
        let label = UILabel()
        label.textColor = UIColor.black
        label.font = UIFont.systemFont(ofSize: 15, weight: UIFontWeightBold)
        label.attributedText = attributedString
        label.sizeToFit()
        self.titleView = label
    }
}
navigationItem.addSpacing(spacing: 2.5)

【讨论】：

【解决方案2】：

将NSAttributedString 设为您链接的问题中的样子
在您的UIButton 上致电setAttributedTitle(_ ,forState:)

试试这个（未经测试）：

let title = agreementButton.titleForState(.Normal)
let attributedTitle = NSAttributedString(string: title, attributes: [NSKernAttributeName: 1.0])
agreementButton.setAttributedTitle(attributedTitle, forState: .Normal)

【讨论】：

我的错。应该只是setAttributedTitle。已编辑

【解决方案3】：

斯威夫特 4

extension UIButton{

    func addTextSpacing(_ letterSpacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: (self.titleLabel?.text!)!)
        attributedString.addAttribute(NSAttributedString.Key.kern, value: letterSpacing, range: NSRange(location: 0, length: (self.titleLabel?.text!.count)!))
        self.setAttributedTitle(attributedString, for: .normal)
    }

}

// Usage: button.addTextSpacing(5.0)

【讨论】：

效果很好！ “NSAttributedStringKey”现在应该是“NSAttributedString.Key”。

【解决方案4】：

不是一个完整的答案，而是一个 GOTCHA 和一个 FIX。

GOTCHA：应用字符间距还会将空格添加到文本的 END。此错误功能/错误意味着居中对齐的文本将无法正确显示。

修复：为属性文本创建 Range 时，从 text.count 值中减去 1（因此忽略字符串中的最后一个字符以实现间距。）

例如由于额外的空间导致不正确的居中：

固定：

[编辑]

在相关说明中，如果您使用 EdgeInsets 在文本周围施加填充，您的 UIButton 子类将需要覆盖 intrinsicContentsSize:

override open var intrinsicContentSize: CGSize {
    let size = super.intrinsicContentSize
    let insets = self.titleEdgeInsets
    let width = size.width + insets.left + insets.right
    let height = size.height + insets.top + insets.bottom
    return CGSize(width: width, height: height)
}

【讨论】：

【解决方案5】：

Swift 5 扩展在这里。

extension UIButton {
    @IBInspectable
    var letterSpacing: CGFloat {
        set {
            let attributedString: NSMutableAttributedString
            if let currentAttrString = attributedTitle(for: .normal) {
                attributedString = NSMutableAttributedString(attributedString: currentAttrString)
            }
            else {
                attributedString = NSMutableAttributedString(string: self.title(for: .normal) ?? "")
                setTitle(.none, for: .normal)
            }

            attributedString.addAttribute(NSAttributedString.Key.kern, value: newValue, range: NSRange(location: 0, length: attributedString.length))
            setAttributedTitle(attributedString, for: .normal)
        }
        get {
            if let currentLetterSpace = attributedTitle(for: .normal)?.attribute(NSAttributedString.Key.kern, at: 0, effectiveRange: .none) as? CGFloat {
                return currentLetterSpace
            }
            else {
                return 0
            }
        }
    }
}

用法：可以在storyboard上设置字母间距，也可以通过代码设置。

button.letterSpacing = 2.0

【讨论】：

【解决方案6】：

Code Different 的解决方案不尊重文本颜色设置。也可以覆盖 UIButton 类以使间距参数即使在情节提要中也可用。这是一个更新的 Swift 3 解决方案：

斯威夫特 3

class UIButtonWithSpacing : UIButton
{
    override func setTitle(_ title: String?, for state: UIControlState)
    {
        if let title = title, spacing != 0
        {
            let color = super.titleColor(for: state) ?? UIColor.black
            let attributedTitle = NSAttributedString(
                string: title,
                attributes: [NSKernAttributeName: spacing,
                             NSForegroundColorAttributeName: color])
            super.setAttributedTitle(attributedTitle, for: state)
        }
        else
        {
            super.setTitle(title, for: state)
        }
    }

    fileprivate func updateTitleLabel_()
    {
        let states:[UIControlState] = [.normal, .highlighted, .selected, .disabled]
        for state in states
        {
            let currentText = super.title(for: state)
            self.setTitle(currentText, for: state)
        }
    }

    @IBInspectable var spacing:CGFloat = 0 {
        didSet {
            updateTitleLabel_()
        }
    }
}

【讨论】：

【解决方案7】：

根据jaya raj 的回答更新 Swift 4。

extension UIButton{
    func addTextSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: (self.titleLabel?.text!)!)
        attributedString.addAttribute(NSAttributedStringKey.kern, value: spacing, range: NSRange(location: 0, length: (self.titleLabel?.text!.characters.count)!))
        self.setAttributedTitle(attributedString, for: .normal)
    }
}

extension UILabel{
    func addTextSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.text!)
        attributedString.addAttribute(NSAttributedStringKey.kern, value: spacing, range: NSRange(location: 0, length: self.text!.characters.count))
        self.attributedText = attributedString
    }
}

extension UITextField{
    func addPlaceholderSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.placeholder!)
        attributedString.addAttribute(NSAttributedStringKey.kern, value: spacing, range: NSRange(location: 0, length: self.placeholder!.characters.count))
        self.attributedPlaceholder = attributedString
    }
}

extension UINavigationItem{
    func addSpacing(spacing: CGFloat){
        let attributedString = NSMutableAttributedString(string: self.title!)
        attributedString.addAttribute(NSAttributedStringKey.kern, value: spacing, range: NSRange(location: 0, length: self.title!.characters.count))
        let label = UILabel()
        label.textColor = UIColor.black
        label.font = UIFont.systemFont(ofSize: 15, weight: UIFont.Weight.bold)
        label.attributedText = attributedString
        label.sizeToFit()
        self.titleView = label
    }
}

【讨论】：

【解决方案8】：

Swift 5 更新，无需强制解包：

我觉得这是一个更好的解决方案，因为我们也满足按钮上的现有属性

func addTextSpacing(_ letterSpacing: CGFloat) {
    let attributedString = attributedTitle(for: .normal)?.mutableCopy() as? NSMutableAttributedString ??
        NSMutableAttributedString(string: title(for: .normal) ?? "")
    attributedString.addAttribute(NSAttributedString.Key.kern, value: letterSpacing,
                                  range: NSRange(location: 0, length: attributedString.string.count))
    self.setAttributedTitle(attributedString, for: .normal)
}

【讨论】：

【解决方案9】：

斯威夫特 5

guard let buttonTitle = button.title(for: .normal) else { return }
    
    let attributedTitle = NSAttributedString(string: buttonTitle, attributes: [NSAttributedString.Key.kern: kernValue])
    button.setAttributedTitle(attributedTitle, for: .normal)

【讨论】：