Swift含有emoji的富文本显示遇到的问题

原来的代码：

let attributedContent: NSMutableAttributedString
NSMutableAttributedString(string: content)
let paragraphStyle: NSMutableParagraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = 7 // 大小调整
attributedContent.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: content.count)) attributedContent.addAttribute(NSAttributedString.Key.font, value: UIFont.systemFont(ofSize: 14), range: NSRange(location: 0, length: content.count))
contentLabel.attributedText = attributedContent
let contentHeight = attributedContent.boundingRect(with: CGSize(width: ltSize.width - 32, height: CGFloat(MAXFLOAT)), options: [.usesLineFragmentOrigin], context: nil).height
contentLabel.frame = CGRect(x: 0, y: 0, width: ltSize.width - 32, height: contentHeight)

原来的效果：1、有些表情显示效果不正确，显示方框和？或其它黑色异样表情；2、行数有问题，显示不完整。

IMG_0515.jpg

修改后的代码：其实只是修改了Range的length，由content.count改成content.utf16.count。

let attributedContent: NSMutableAttributedString
NSMutableAttributedString(string: content)
let paragraphStyle: NSMutableParagraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = 7 // 大小调整
attributedContent.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: content.utf16.count)) attributedContent.addAttribute(NSAttributedString.Key.font, value: UIFont.systemFont(ofSize: 14), range: NSRange(location: 0, length: content.utf16.count))
contentLabel.attributedText = attributedContent
let contentHeight = attributedContent.boundingRect(with: CGSize(width: ltSize.width - 32, height: CGFloat(MAXFLOAT)), options: [.usesLineFragmentOrigin], context: nil).height
contentLabel.frame = CGRect(x: 0, y: 0, width: ltSize.width - 32, height: contentHeight)

正确显示的效果：

IMG_F38FDE0515E8-1.jpeg

还有一种方式，将Swift的字符串转成OC的NSString

let attributedContent: NSMutableAttributedString = NSMutableAttributedString(string: content)
let paragraphStyle: NSMutableParagraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = 7 // 大小调整
attributedContent.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: (content as NSString).length))
attributedContent.addAttribute(NSAttributedString.Key.font, value: UIFont.systemFont(ofSize: 14), range: NSRange(location: 0, length: (content as NSString).length))
contentLabel.attributedText = attributedContent
let contentHeight = attributedContent.boundingRect(with: CGSize(width: ltSize.width - 32, height: CGFloat(MAXFLOAT)), options: [.usesLineFragmentOrigin], context: nil).height
contentLabel.frame = CGRect(x: 0, y: 0, width: ltSize.width - 32, height: contentHeight)

分享原因：NSString是由UTF-16单元构成,.length方法返回的是基于UTF-16的长度。Swift的count返回的只是Unicode字符个数,而Swift有专门的utf16.count是对应NSString的.length方法。