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。

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)];

对于多行文本，可以使用NSAttributedString设置左右边距。

NSMutableParagraphStyle *style =  [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
style.alignment = NSTextAlignmentJustified;
style.firstLineHeadIndent = 10.0f;
style.headIndent = 10.0f;
style.tailIndent = -10.0f;   

NSAttributedString *attrText = [[NSAttributedString alloc] initWithString:title attributes:@{ NSParagraphStyleAttributeName : style}];  

UILabel * label = [[UILabel alloc] initWithFrame:someFrame];
label.numberOfLines = 0;
label.attributedText = attrText;

以下是Swift 5采用的上述示例:

extension UILabel {
    func setMargins(margin: CGFloat = 10) {
        if let textString = self.text {
            var paragraphStyle = NSMutableParagraphStyle()
            paragraphStyle.firstLineHeadIndent = margin
            paragraphStyle.headIndent = margin
            paragraphStyle.tailIndent = -margin
            let attributedString = NSMutableAttributedString(string: textString)
            attributedString.addAttribute(.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: attributedString.length))
            attributedText = attributedString
        }
    }
}

为了消除单行标签的垂直填充，我做了:

// I have a category method setFrameHeight; you'll likely need to modify the frame.
[label setFrameHeight:font.pointSize];

或者，不带类别，使用:

CGRect frame = label.frame;
frame.size.height = font.pointSize;
label.frame = frame;

这是我发现的最简单的方法。这对我来说很有魔力。

UIView *titleSection = [[UIView alloc] initWithFrame:CGRectMake(0, 0, screenWidth, 100)];
[titleSection addSubview:titleSection];

UILabel *label = [[UILabel alloc] initWithFrame:CGRectInset(titleSection.frame, PADDING, 0)];
[titleSection addSubview:label];

设置标签的textAlignment属性为NSTextAlignmentRight并增加它的宽度。