也许你可以试试这段代码

CGRect frame = btn.titleLabel.frame;
int indent = 20;
int inset = 20;
[btn.titleLabel setFrame:CGRectMake(frame.origin.x+inset,frame.origin.y,frame.size.width+indent,frame.size.height)];

对于这样一个简单的情况，子类化有点麻烦。另一种方法是将没有背景设置的UILabel添加到有背景设置的UIView中。将标签的x设置为10，并使外部视图的大小比标签宽20个像素。

这适用于多行标签:

class PaddedLabel: UILabel {
    var verticalPadding: CGFloat = 0
    var horizontalPadding: CGFloat = 0

    override func drawText(in rect: CGRect) {
        let insets = UIEdgeInsets(top: verticalPadding, left: horizontalPadding, bottom: verticalPadding, right: horizontalPadding)
        super.drawText(in: UIEdgeInsetsInsetRect(rect, insets))
    }

    override var intrinsicContentSize: CGSize {
        get {
            let textWidth = super.intrinsicContentSize.width - horizontalPadding * 2
            let textHeight = sizeThatFits(CGSize(width: textWidth, height: .greatestFiniteMagnitude)).height
            let width = textWidth + horizontalPadding * 2
            let height = textHeight + verticalPadding * 2
            return CGSize(width: frame.width, height: height)
        }
    }
}

我认为UILabel类没有设置边距的方法。为什么不把标签的位置设置在需要的位置?

见下面的代码:

UILabel *label = [[UILabel alloc] init];
label.text = @"This is label";
label.frame = CGRectMake(0,0,100,100);

如果来自接口构建器，则按以下方式定位Label:

yourLabel.frame = CGRectMake(0,0,100,100);

如果是单行，只需在左侧添加空格，超过一行的填充将再次为0。

[self.myLabel setText:[NSString stringWithFormat:@"   %@", self.myShortString]];

在Swift 3中，你可以通过创建UILabel的子类来达到你想要的效果。在这个子类中，你必须添加一个UIEdgeInsets属性，并覆盖drawText(In:)方法，intrinsicContentSize属性(用于自动布局代码)和/或sizeThatFits(_:)方法(用于Springs和Struts代码)。

import UIKit

class PaddingLabel: UILabel {

    let padding: UIEdgeInsets

    // Create a new PaddingLabel instance programamtically with the desired insets
    required init(padding: UIEdgeInsets = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)) {
        self.padding = padding
        super.init(frame: CGRect.zero)
    }

    // Create a new PaddingLabel instance programamtically with default insets
    override init(frame: CGRect) {
        padding = UIEdgeInsets.zero // set desired insets value according to your needs
        super.init(frame: frame)
    }

    // Create a new PaddingLabel instance from Storyboard with default insets
    required init?(coder aDecoder: NSCoder) {
        padding = UIEdgeInsets.zero // set desired insets value according to your needs
        super.init(coder: aDecoder)
    }

    override func drawText(in rect: CGRect) {
        super.drawText(in: UIEdgeInsetsInsetRect(rect, padding))
    }

    // Override `intrinsicContentSize` property for Auto layout code
    override var intrinsicContentSize: CGSize {
        let superContentSize = super.intrinsicContentSize
        let width = superContentSize.width + padding.left + padding.right
        let height = superContentSize.height + padding.top + padding.bottom
        return CGSize(width: width, height: height)
    }

    // Override `sizeThatFits(_:)` method for Springs & Struts code
    override func sizeThatFits(_ size: CGSize) -> CGSize {
        let superSizeThatFits = super.sizeThatFits(size)
        let width = superSizeThatFits.width + padding.left + padding.right
        let heigth = superSizeThatFits.height + padding.top + padding.bottom
        return CGSize(width: width, height: heigth)
    }

}

下面的例子展示了如何在UIViewController中使用PaddingLabel实例:

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var storyboardAutoLayoutLabel: PaddingLabel!
    let autoLayoutLabel = PaddingLabel(padding: UIEdgeInsets(top: 20, left: 40, bottom: 20, right: 40))
    let springsAndStructsLabel = PaddingLabel(frame: CGRect.zero)
    var textToDisplay = "Lorem ipsum dolor sit er elit lamet."

    override func viewDidLoad() {
        super.viewDidLoad()

        // Set autoLayoutLabel
        autoLayoutLabel.text = textToDisplay
        autoLayoutLabel.backgroundColor = .red
        autoLayoutLabel.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(autoLayoutLabel)
        autoLayoutLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 30).isActive = true
        autoLayoutLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        // Set springsAndStructsLabel
        springsAndStructsLabel.text = textToDisplay
        springsAndStructsLabel.backgroundColor = .green
        view.addSubview(springsAndStructsLabel)
        springsAndStructsLabel.frame.origin = CGPoint(x: 30, y: 90)
        springsAndStructsLabel.sizeToFit()

        // Set storyboardAutoLayoutLabel
        storyboardAutoLayoutLabel.text = textToDisplay
        storyboardAutoLayoutLabel.backgroundColor = .blue
    }

    // Link this IBAction to a UIButton or a UIBarButtonItem in Storyboard
    @IBAction func updateLabelText(_ sender: Any) {
        textToDisplay = textToDisplay == "Lorem ipsum dolor sit er elit lamet." ? "Lorem ipsum." : "Lorem ipsum dolor sit er elit lamet."

        // autoLayoutLabel
        autoLayoutLabel.text = textToDisplay

        // springsAndStructsLabel
        springsAndStructsLabel.text = textToDisplay
        springsAndStructsLabel.sizeToFit()

        // storyboardAutoLayoutLabel
        storyboardAutoLayoutLabel.text = textToDisplay
    }

}